Will the 8-1/2 “ carrier from a 91 to 95 Caprice work in the GN rear? I think they are 30- spline so the axles will need to be changed. The Caprice has ABS sensor on the pinion, but I wonder if the carrier is the same.
If you plan on replacing the carrier bearings then get them for the '88 and newer. The OD of the outer race is the same but the bearing size and ID of the inner race are different.
Moser has 30 spline axles readily available for our cars.
I believe the Auburn uses "cone" style side gears that dig into the case and after time they get dug in too far into the case and they're done. You need to find a "clutch" type differential. When you look at the diff from either side there will be a hole you can see what looks like friction plates used inside an automatic transmission. Also I believe the clutch style uses a piece of spring steel shaped like an S to put preload on the side gears while the cone type uses a pair of side plates that house 5 small coil springs