The overall design is essentially the same, the difference is the size. The 60 has a 9.75" ring gear, the 70 has a 10.5" ring gear. Both will be full floating in a 3/4 ton, while I have seen semi float 60s (Hemi Chryslers, GMC/Chevrolet 1/2 tons, many late model 3/4 ton vans from the Big 3), I have never come across a semi float 70. The easy way to tell what you have is to look for a "60" or "70" cast into the center section. Usually, it can be found either on the top of the pinion snout or on the rear face of the housing, next to where the cover mounts.
