So here is the cool part. You can easily find an 8.8 with 4.10s and the D30 out of a 4cl XJ will have 4.10s. If you have a low pinion late model D30 XJ, and need to change gear ratio for bigger tires, this is your chance to upgrade to a high pinion with 4.10s, which is stronger. Plus, you get to rebuild it while you drive, then swap both at the same time! If you already have 4.10 front, or you need 4.56, you will have to change at least the gears in the D30. You may be able to find a 8.8 with 4.56s if you look real hard. Look for an 8.8 with disks, limited slip, and 30 spline axles our of a 1999 or newer Ford Explorer. I did this to my 2000. I am running 31s with a RE 3.5+ lift and it works real well. I am using a stock front drive shaft for my rear shaft as well (4.0, AW4,231, previous rear was C8.25). Hope this helps. Good luck! JM