The first thing you want to do is to determine exactly what differential ratio you have. Go look in your glove box for a label and look at the 3 digit codes Look for the ones starting with G?? I'm an guessing you will have one of these:
G80 Differential, automatic
GT4 Rear axle, 3.73 ratio
GT5 Rear axle, 4.10 ratio
GU6 Rear axle, 3.42 ratio
and possibly two with G80 (locking differential).
You need to match whatever you have now with those RPO codes.
Then you can start your search through rebuilders, Junk yards, and disassemblers.
G80 Differential, automatic
GT4 Rear axle, 3.73 ratio
GT5 Rear axle, 4.10 ratio
GU6 Rear axle, 3.42 ratio
and possibly two with G80 (locking differential).
You need to match whatever you have now with those RPO codes.
Then you can start your search through rebuilders, Junk yards, and disassemblers.