489 case with cone style sure grip rebuild
I'll give you a bump because I'm getting ready to do the same thing. I'm farming it out to a friend who knows WAAAAY more than myself, but I think it's just and matter of having the cones milled down a bit. RRR did a nice write up on it a while back.
How To Recondition a Sure Grip Cone
Here is the Dr. Diff kit if anyone wants to check it out.
Mopar 8 3/4" Cone Sure-Grip Shim Pack