Panel replacement on a rotten truck

[GMtrucknut!!]

Okay I am sure we have all put at least one set of inside steps and rocker panels on a 55-59 chevy truck .With the standard being measure everything brace the jams and drill out your spotwelds then re-measure and weld in the new panels but what do you do when your floor pans and ,cab mounts, etc are also bad enough that the front portion of the cab and door openings are not square to begin with ? Currently I am trying to square up a friends but its bad enough that I am measuring mine to get his close,is this a good idea or am I wasting my time?

[OrrieG]

I would measure his frame to get diagonals and squared up measurements of the cab mounts. Diagonals should be the same if the mounts are square. The back cab mounts are in the channel, hopefully it is intact, check them to make sure they will align with the frame mounts. Using the frame measurements you should be able to locate where the front mounts go by swinging a diagonal and square radius from each back hole, basic geometry.

If you only have one good hole location in the cab floor to start with you need to use the 3-4-5 triangle to get a right angle and at least one other hole, preferably the back mounts. From there swing the diagonals, etc. This is the same principle carpenters use to layout walls so they are square and parallel.

From there you just need to get accurate measurements, or better yet, get big pieces or cardboard like refrigerator boxes and make a template off of your known good truck floor. Start installing metal, just tacking until you can get to a point to hang the doors, that will tell you if you are close and is the most critical aspect. Do not rely on the patch panels being correct, most need some massaging to work.

You will also need to make sure every thing is level side to side, front to back and across the diagonal too. If it is that far gone I would be using the leveled frame to work on. I would also be taking vertical diagonal measurements across the cab to make sure the side jambs stay the same and do not get racked. Remember just welding can pull metal out of shape too. Once you are happy, do the finish welding, skipping around and keep taking measurements as you go.

Lots of work but doable, just need to keep track of alignment as you go.

[mr48chev]

If you don't have one, a copy of the Assembly manual for that truck is a pretty good investment. Amazon.com: 1955-1959 Chevrolet, GMC Truck...
I've got one for my AD truck and it gives exact measurements and shows a lot of detail on the assemblies. You do have to weed through all the stuff for the different models to find the right page at times but the book pays for it's self pretty quickly for most of us.

I know I sound like a broken record to some of the guys when I am always pushing buying manuals but I learned a long time ago it isn't what you know but knowing where to find the info that counts.

[GMtrucknut!!]

Well with the assembly manual and careful measurements I have got it all square now I have to finish weld the new panels and call it a day thanks OrrieG on your advice !!