An Olds 12 bolt is not necessarilly the same as a Chevy 12 bolt and may not have the same reputation. There is a number stamped on the axle, facing forward on the passenger side which can be used to identify it. I need to do some research on this and promise to look it up. Sorry I don't know it by heart and am not well versed on this subject but do know for sure about my first statement. Hope I can get the info you need.
I found this link, hope it helps:
http://www.442.com/oldsfaq/ofdif.htm#Differentials