67 3/4 ton rear axle to 72 1/2 ton frame

[odog]

How hard is it to put a 67 3/4 ton axle with springs on a 1972 1/2 ton frame. I would like the axle and springs. The 3/4 ton measure 57 inches eye to eye, and the 72 measues 52 eye to eye. Do I have to relocate the perches, do I get springs from a differnet truck? I have a 76 3/4 ton that I may be able to use the springs from. Im just fishing for Ideas. The truck is my firewood getter and I really dont like overloading it. A full cord and half of wood is a lot of wieght and I am thinking 3/4 ton axles and springs would help out.