Square-body buyer's guide: what rust actually costs

Square bodies have gone from cheap to genuinely valuable in about a decade, and the ones left have all been sitting somewhere. What kills them is almost never the drivetrain — a 350 will run badly for decades. It is the structure. Here is what to check, roughly in order of what it costs to put right.

011. Cab corners and rocker panels

Look here first, before anything else. Kneel down and look at the bottom of the cab behind the door. Cab corners rust from the inside, because the drain channel above them fills with leaves and holds water against the metal. By the time it shows on the outside, the inner structure has usually gone too. Patch panels are inexpensive; the labour to cut, fit and blend them is not, and if the rocker has gone then the cab mount is often next. Press hard with your thumb along the bottom of the rocker. If it flexes, it is thin. If it crunches, walk away or price a full rocker.

022. Cab mounts

Get underneath. There are six, and the front two take the worst of it because the front wheels throw water directly at them. A collapsed cab mount lets the cab settle onto the frame. You see it as doors that will not shut squarely and a gap along the top of the door that tapers front to back. People spend entire weekends adjusting hinges chasing a problem that has nothing to do with the doors. The bushings themselves are cheap. If the mount *pockets* in the cab floor have rotted through, that is a different and much larger job.

033. The bed floor and the front bed panel

The bed floor rots wherever the wood or the mat held moisture. That is straightforward — there are good reproduction floors and it is bolt-in work. The front bed panel, between the bed and the cab, is the one to check properly. It traps everything that blows into the gap, it is invisible unless you look for it, and it is an awkward panel to replace well.

044. Steering box and linkage

Sit in it and rock the wheel with the engine off. More than about two inches of free play at the rim means something is finished — usually the idler arm, sometimes the box. Then get under the front and have someone rock the wheel while you watch. You are looking for vertical movement in the idler arm, which is the common failure and an inexpensive fix. Play inside the box itself is a bigger job, though a rebuilt box is readily available.

055. Front coil springs

A truck that sits nose-down has springs that have taken a set, not tired shocks. Twenty-five years under a big block does that. Measure from wheel centre to arch lip on both sides, front and rear. A truck sitting low at the front, or sitting unevenly side to side, needs springs. Fitting new shocks to collapsed springs achieves nothing at all, and it is the most common misdiagnosis in the hobby.

066. Wiring

Open the fuse box and look at the harness where it passes through the firewall. Square-body harnesses are simple and repairable, but forty years of previous owners adding stereos, lights and trailer plugs leaves a mess of scotch-locks and twisted joints. A butchered harness is not a deal-breaker but it is a full weekend to sort properly, and an under-dash fire if you do not.

07What is not worth worrying about

The engine, unless it is knocking. A small block that smokes on start-up needs valve seals — a day's work with the heads on. One with low compression across the board is a rebuild you were probably going to do anyway, and it is the best-supported engine in the world. The interior. Every piece is reproduced — carpet, seat, dash pad, door panels, headliner. A shabby interior is a bargaining chip, not a problem. Chrome and trim. Reproduced, and the current quality is genuinely good.

08The summary

Buy the straightest, driest body you can find and accept whatever is wrong mechanically. Rust is the expensive thing. Everything bolted to the frame can be replaced from a catalogue over a few weekends. The cab cannot.