Squarebody Rust Repair Panels: Cab Corners, Rockers, and Floor Pans Buyer’s Guide

If your 1973-1987 Chevy or GMC truck is starting to bubble at the bottom of the doors, the back of the cab, or the floor under your boots, you are not alone. Rust is the number one enemy of these trucks, and the right squarebody rust repair panels are the difference between a clean, lasting fix and a patch job that comes back in two seasons. This buyer’s guide walks you through the common rust spots, the panel options available, and exactly how to match the right part to your cab style, drivetrain, and model year so you order correctly the first time.

Quick answer: Squarebody trucks rust most at the cab corners, rocker panels, cab floor pans, lower doors, and bed floors. For small, isolated rot, buy individual patch panels. For a whole area that is gone, buy full drop-in floor assemblies or full cab corners. If several areas are rusted at once, a multi-piece rust repair kit is usually the best value. Always match the panel to your cab style (regular, extended, crew, or Blazer), your 2WD or 4WD configuration, and your 1973-80 or 1981-87 year range.

Where squarebody trucks rust the most

Before you shop for squarebody rust repair panels, it helps to know the usual suspects. Water, road salt, and trapped debris collect in the same places on nearly every 73-87 Chevy and GMC truck. The most common rust areas are cab corners, rocker panels (both inner and outer), cab floor pans, lower doors, bed floors, the rear window channel, and the lower front fenders. Most of these are low on the body where moisture sits, or in hidden cavities that never fully dry out.

If you are still figuring out how bad your truck is, start with our full squarebody rust spots repair guide, which shows you where to look and how to tell surface rust from structural rot. Knowing the scope of the damage tells you whether you need a single patch or a full assembly, and that decision shapes everything else you buy.

It also pays to think about rust in groups rather than one spot at a time. Water that rots a cab corner usually tracks down into the rocker and the floor behind it, so when you find damage in one area, inspect the neighbors before you order. Buyers who tackle the whole lower section at once almost always spend less and fit better than those who chase one hole, finish, and discover the next one a month later. A quick, honest assessment up front keeps your parts list accurate and your project on schedule.

Cab corners: what to look for and how to pick the right one

Cab corners are the lower rear sections of the cab, right behind the doors where the cab meets the bed. They are one of the first areas to rust because mud and moisture pack into the seam. When you inspect yours, check both the outer skin and the inner structure. If the metal flexes or flakes when you press it, the corner needs replacing, not just filling.

There are also a couple of corner heights to be aware of. Some squarebody owners only need a short corner that covers the lower few inches, while trucks with rust creeping up toward the window line do better with a taller corner that gives you more good metal to weld to. Look at how high the bubbling reaches, and buy a corner that extends at least an inch past the worst of it so your weld lands on solid steel. Ordering a corner that is too short is one of the most common reasons a repair looks wavy afterward.

Cab corners are side-specific, so you must order a left (driver) and a right (passenger) piece. They also differ by cab style. A standard or regular cab, an extended or bonus cab, a crew cab, and a Blazer or Jimmy each use a different corner shape, so confirm your cab type before ordering. For step-by-step install instructions, see our cab corner replacement guide and our companion how to replace cab corners walkthrough. This buyer’s guide is only here to help you choose the right part; the install steps live in those guides.

Rocker panels: inner versus outer

Rocker panels run along the bottom of the cab beneath the doors, and they are a structural part of the body, not just trim. Squarebody rockers come in two layers. The outer rocker is the visible skin, and the inner rocker is the hidden support behind it that carries real load. Many trucks that look like they only need an outer skin actually have a rusted inner rocker too, which is why it pays to probe deep before you buy.

If only the outer skin is pitted, an outer rocker patch panel will do. If the inner structure is compromised, buy both inner and outer pieces so the repair is strong and the door gaps stay true. Rockers are also side-specific and vary by cab length, so match them to your cab the same way you would cab corners. Our rocker panel replacement guide covers the install in detail.

Because the rocker ties the cab corner and the floor together, these three parts are frequently bought as a set. If you have rust in one, brace the door opening before cutting so the cab does not shift while the structural metal is out. That is an install detail covered in the guide above, but it is worth knowing at the buying stage, because it may change whether you choose to replace one rocker or do both sides at once for a balanced, square cab.

Cab floor pans: patch versus full, 2WD versus 4WD, and cab style

The cab floor pan is where buyers make the most ordering mistakes, so slow down here. First, decide between a patch and a full pan. If the rust is a small, contained hole, a floor pan patch panel saves time and money. If the floor is soft across a wide area, or the supports underneath are gone, a full drop-in floor assembly gives you a cleaner, stronger result.

Second, and this is critical, 2WD and 4WD floor pans are not the same. The transmission and transfer case tunnels differ, so a 4WD pan will not sit correctly in a 2WD cab and vice versa. Third, floor pans vary by cab style, since a regular cab, extended cab, and crew cab each have different floor lengths and seat mounting areas. Confirm all three (patch or full, drivetrain, and cab style) before you add to cart. When you are ready to install, follow our floor pan replacement guide or the detailed how to replace floor pans walkthrough.

Bed floors, lower doors, and other panels

Two more areas round out most squarebody rust repairs. Bed floors rust from debris and standing water, and you can buy individual bed floor sections or complete bed floor kits depending on how much is left. Lower doors rot at the bottom seam, and you can fix them with lower door skin patch panels rather than replacing the entire door shell. Door bottoms rust from the inside out because the drain holes clog, so a patch panel plus clearing those drains often outlasts the original metal. Related pieces like inner wheelhouses and tailgate panels often need attention at the same time, since they sit in the same wet zones.

A few real examples from our catalog: the left inner wheelhouse panel is a common follow-on repair when bed floors go, and the fleetside tailgate panel replaces a rotted or dented tailgate skin. For broader exterior work, our body panel guide for fenders, doors, and hood explains how these pieces fit together, and hardware like a left hood hinge is often worth refreshing while you have the front end apart.

Patch panel vs full assembly vs rust repair kit: how to choose

The three main types of squarebody rust repair panels each suit a different situation. Patch panels are small sections that cover a specific hole, and they are the cheapest and fastest option for light, isolated rust. Full assemblies, such as a complete floor half or a full cab corner, replace an entire area at once and give the strongest, most factory-correct result when rot is extensive. Rust repair kits bundle several matched pieces together, which is ideal when a truck is rusted in multiple spots and you want everything to fit as a set.

Here is a quick comparison to help you decide.

Option	Best for	Rust severity	Skill / time	Relative cost
Patch panel	One small, contained hole	Light to moderate	Beginner friendly, quick	$
Rust repair kit	Several rusted areas at once	Moderate to heavy	Intermediate, moderate time	$$
Full floor assembly	A whole area that is gone	Heavy or structural	Advanced, most time	$$$

What to check before buying squarebody rust repair panels

Three details decide whether a panel fits like it should. First, steel gauge. OEM-quality squarebody rust repair panels are stamped in the correct thickness so they weld cleanly and hold shape. Thin, flimsy panels warp under the torch and never line up right. Second, OE contour. A good panel matches the factory stampings, body lines, and curves, so your door gaps and body seams stay even after the repair. Third, the year and cab match. Confirm your truck is 1973-80 or 1981-87, because several panels changed between those ranges, and double-check your cab style and 2WD or 4WD setup for anything structural.

When in doubt, measure the area you are replacing and compare it to the product listing. A few minutes of checking saves a return and a stalled project. Our FAQ page answers more fitment questions if you are unsure.

One more buying tip: order a little extra coverage rather than exactly what the rust shows today. Rust almost always extends past what you can see, and having a panel that reaches into solid metal gives you clean edges to weld. It is far easier to trim a slightly larger panel to fit than to stretch an undersized one across a gap. When you pair the right size with the correct gauge and contour, your squarebody rust repair panels drop in close to factory position and need far less filler to finish.

Frequently Asked Questions

Where do squarebody trucks rust the most?

The most common rust areas are cab corners, rocker panels (inner and outer), cab floor pans, lower doors, bed floors, the rear window channel, and lower front fenders. These are all low spots or hidden cavities where water, salt, and debris collect and sit. Checking these areas first tells you how much repair your truck really needs.

Should I use patch panels or full floor pans?

Use a patch panel when the rust is a small, contained hole surrounded by solid metal. Choose a full floor pan assembly when the floor is soft across a wide area or the supports underneath are rotted. A full pan costs more and takes more skill, but it gives a stronger, more factory-correct result when the damage is extensive.

Are squarebody cab corners side-specific?

Yes. Cab corners are left and right specific, so you need to order the correct side, or both if you are repairing each corner. They also differ by cab style, meaning regular cab, extended cab, crew cab, and Blazer corners are not interchangeable. Confirm both the side and the cab type before ordering.

Do 2WD and 4WD squarebody floor pans fit the same?

No. The 2WD and 4WD floor pans have different transmission and transfer case tunnel shapes, so they are not interchangeable. A 4WD pan will not seat correctly in a 2WD cab, and the reverse is also true. Always match the floor pan to your truck’s drivetrain along with its cab style.

Get the right panels for your squarebody

Ready to stop the rust and bring your truck back to solid metal? Browse our full selection of squarebody body panels to find cab corners, rockers, floor pans, and patch panels stamped in OE-quality steel and matched to your year, cab, and drivetrain. You can also explore the complete shop for everything else your restoration needs. Order the correct panel the first time, follow the linked install guides, and your 73-87 Chevy or GMC will be back on the road and built to last.