This has nothing to do with the box wall alignment, but with the tailgate.
I asked my wife to make me two fabric socks for the tailgate chain & hooks. The original plastic socks that came with the truck were just ugly, stiff and not nice.
This should make a difference (could have gotten a little heavier fabric, well, next time).
~ NORTH OF 49TH 1948 GMC Model 9434 Frame rebuild 1953 Chevrolet 1314 1/2 ton rebuild Follow along it the DITY Bay