The 3/4 ton is a rough riding s.o.b. for sure. Used to be a guy here who would make a 1/2 ton out of the 3/4 putting in ifs and a nova or camaro rear with lighter springs. I haven't looked into the spring issue, my plans are to be able to haul loads with mine. On the differential you might look at the late model 14 bolt full floater. There are a lot with 3.73 gears, I was told it also comes in 3.42. I never got back to checking on widths, but you should be able to use a narrow housing with 4x4 wheels, which have a deep setback and still fit in the wheel well. If you go with the 67-72 the best you will find is going to be 4.10 without a lot of searching. The best they came with was 3.73, which would be acceptable with the 700r4.
