Here we have a good used takeout GM G80 Factory limited slip / post / automatic locker for the venerable and prolific GM 10.5" Corporate 14 bolt rear axle.
Fits 1973 - 2012 with the bolt in pinion support.
No real way to test these. Everything turned freely and no metal in the gear oil.
This is the "Fast" series carrier that had 4.10 gears on it. So 4.10 and numerically lower (3.73 etc) is the split.
Best price, in stock and ready to ship!
Exact item pictured WITH carrier bearings and races, full set of ring gear bolts.