X3. Cass will hook you up. I found an old power lock and cass hooked me up with 1 piece side gears and new clutches, and a bearing kit. I had a machine shop install the carrier bearings and did the rest my self. 3.23 is a good street gear. I'd use them if they are in good shape. As mentioned, measure backlash before you disassemble, then set the gears to that same spec when reinstalling, to minimize the chance of noisy gears.
