61 3/4 ton to 1/2 ton questions

[68c10owner]

My buddy was given a 1961 3/4 ton. He wants to make a shortbed out of it and thats no problem but what all do i have to do to convert it from 3/4 ton to 1/2 ton? He said it has coi springs and the trailing arms in the rear with some sorta half a leaf helper spring. Can we just put a 1/2 ton diff. under there with regular springs? The front will most likely get swapped for a 73-87 crossmember and we will remove the X frame and box the frame a little more. He doesn`t know much about these trucks so I`ll most liley be doing most of the work. Funny thing is he`s the one that got me into hot rods 20 years ago and now he dosn`t even know where to start,lol. Help me out guys.