You can change ratios within the Spicer housings, however there is the complication that there is 2 different offsets for the diff carrier, for higher or lower ratios. Typically you can change out ring and pinion sets from 3.92 to 5.38 with the same carrier and lower than 3.92 with the other offset carrier. You would need to bone up on setting backlash with a dial indicator to get it right, which is not that easy at first if you change out carriers. A bearing puller, a big vise and a die grinder would be a help also. Just changing out the ring and pinion still requires some careful measuring, and setting shims. Or find a local mechanic or differential shop to get it right. Lots of shop manuals have differential rebuilding in them. Check out a Spicer or a Dana section and see if you understand it, and go from there. Most of my experience is rebuilding blown plow truck fronts and rears at the truck salvage yards, as well as my own Jeep diff shop business in the 70's and 80's. A little bit of bigger stuff mixed in too. good luck diggerG