9-bolt

From Camaro Wiki

The third generation Camaros were available with an optional Borg Warner 9-Bolt rear end. It was known as the Aussie Posi because it was manufactured in Australia. This rear is considered to be much stronger than the 10-Bolt that was on most third and 4th gen cars, however they are also more difficult (and expensive) to find parts for. It is believed that GM quit offering the rear due to production costs.

There is a ton of useful info about this rear end here: [1]