I don't mean to hijack this thread but I'm working on the same project right now. Before I started cutting any boards, I spent some time laying out the dimensions in AutoCAD. First thing I found was the gmcpauls dimensions are grossly inaccurate for a 1950 Chevy truck. Maybe those are the dimensions for a GMC but don't use those for a Chevy. Mar-K have good dimensions.
My question has to do with the outer most boards. Do those boards slide under the angle strip and stop at the bolts or do the boards go all the way under the angle strip to the bedside and the bolts bolt through the boards? Obviously that will make a 1" difference in those two boards.
If anyone needs specific dimensions for the board widths, let me know. I can send a section with dimensions (but verify dimensions on your truck before cutting anything).