Drivetrain - LS1GTO.com Forums
Go here and see if you can find some information. There are a few guys on there that order Borg Warner parts directly from Australia. That is definately a Borg Warner differential that you have. The '04 to '06 GTO, some 3rd gen Camaros and Trans AMs from '85 to '90 and the G8 all used the Borg Warner differentials.