Putting a short bed on a long bed frame

I am beginning building up my '78 stepside truck. I am getting ready to tear down to the frame, swap the axles and engine, and build it back up. I am looking at buying a 3/4 ton donor truck to do this and got to thinking about swapping bodies instead of running gear. What it be worth it to shorten the frame and use it instead of my 1/2 ton frame?
If I did this, I imagine I would have to build new mounts for the bed, but am not sure.
Would there be value in doing it this way, or would it just be a major headache? I know I would end up with a stronger frame, but are there other benefits as well?