JoeR
I have the same bed and side boards, It looks like you'res has been modified [the wood sides]anyway. I may be able to take some pics of mine so you will know what you are in for if you rebuild it. The bed boards on mine went away as soon as it got damp, the metal strips between boards looks to be about the same shape in cross section as the half ton but wider and longer [ mine were not good] . The front corners on mine were shortend for some reason ??? you'res look full size. there is a frame around a opening at the cab back window, I can get a good pic of this. The bed boards are about a inch thick but 2x6 2x8 possibly could work BUTT????? Good luck with you're project you have a long way to go before the bed
T-ruck