Someone will correct me if I'm wrong, but if you have the 4.0 then you have the best axles offered in a ranger. The d35 and a 28-spline 8.8. These should both be capable of 35's, i think? The rear could be swapped out for 31-spline 8.8, from an explorer, if you wanted a little extra insurance and the 95 and newers have discs as already said.