Swapping out the axle is one method. The 1 ton frame is actually 1/2" narrower than the 1/2 ton. With that being said, the 1 ton has 2" wide springs and the 1/2 ton has 1.75". In theory the 1/2 ton axle should line up. Like 80 Grit said, you could enlarge the holes on your axle. I'm not a fan of that idea, there's too much that can go wrong.
Another idea is to use 1/2 ton spindles and hubs. You would have to have a bushing made because the 1/2 ton king pin is .86" and the 1 ton is .92". I don't know if you could ream the 1/2 ton spindle out to work or not. There may not be enough material.
http://chevy.oldcarmanualproject.com/chevyresto/4971.htm
