I took a few measurements but honestly, I've come to the conclusion that trucks made during the 70s were close enough builds. The guys putting them together welded things in place to fit. The measurments have been all over the place.
My plan is to get the cab portion back on the frame and then fit the doors. I'll then get the bed put back on and then put the bedside panels on. I think it will be a lot of trial and error regardless of bracing and the old measurments. Which, by the way, is going to be the process anyway because the aftermarket panels will always be a little different that original.
It might be a different story if I was ONLY replacing one bedside panel or one floor pan. But I'm replacing so much that I don't think bracing is really going to do much good. And honestly I think it might make things more frustrating.
I'm probably wrong but good news is we are going to find out!