swapping bedsides

[67mater]

Any problem with buying a rust free 1977 full size fleet bed with the intention of cutting my 67 bed sides off and welding them on the new(er) bed to go on my 67 K20? Would just a floor swap be worthwhile? anybody know how the floors compare? how the cross sills, mounting holes compare? I can get a 77 bed that has had a topper on it for $125 so it seems worth trying to swap outer skins. Anybody know a reason I shouldn't? I know the inner taillight housing would be tricky, but this seems like a cheap way to get a solid bed.