Hideeho
I used to run the rpm cups & really liked them. I picked up the JC cups to give them a try. I had issues when I first tried them because I put the bent cups on the inside rear for extra clearance around the bb shocks. That did not work at all. Once I found out that was the problem & put the bent cups on the out side rear I haven't had any pop offs since. Either are great choices, but the JC cups have the holes & come with enough in 1 kit for 2 vehicles with extras.

To adjust the dif, look on the 1st page for the video about the handy dif tool. This will allow you to adjust your dif (front & rear) without removing any cups. It also can be used to remove the inside camber link ball studs easily plus it can be used to set you slipper. This is a tool that EVERYONE with a b44 needs to have in their tool box.