Yea, I don't see why you couldn't just shorten the back half.. hell, i'd just cut a chunk out from just behind the cab, then drag the back half forward and weld it back on.. then get a drive shaft to match, and voila! You got a 1/2 ton length with a 1 ton suspension!
If you're talking about an old 'c' channel frame, i'd go ahead and 'box' the frame a few feet in either direction of the weld.
Now if you already have a 1/2 ton frame, most parts are a direct swap between a 1 ton and a 1/2 ton.. altho depending on year, the front fenders and perhaps the hood might be larger than the 1/2 ton design.
What year truck(s) are we talking about?
