You didn't mention tire & rim size - which could play a big role (in durability & rpms). Stock jeep tires are like 235/75/15's which are roughly 28" or so in height. I personally wouldn't run anything larger than 31's with a stock D30. The 2 piece rear axles would have to go to - they were prone to failure on stock setups. The AMC20 will hold up, but might need bracing if you plan to offroad (weak tubes).