1980yota

ok i have a 1980 toyota 4x4 and the driver side frame is rusted BAD!! as in a pop the clutch my bed twits and hit the cab, BAD!! so i found a 1980 2wd LONG bed now. this idea may sound stupid or make sence and be a good idea(advice would be great). take the short bed frame and cut it in half where the rust starts and do the same to the 2wd excluding the rust dont need no more rust. lol and weld the front 4wd and rear 2wd togather. Now i know the bed mounts would be moved but what else would move . OR could i just shorten the long bed frame? thank for any info.