Originally Posted by big1
The "GT" rear was a " Nodular" case, it had an "N" cast into it, located at the top center. It could still be a standard 9in. thou and it was a very strong unit.
If you can get under the car. Take a 3/8 drive ratchet and shallow socket with you. If you CANNOT put the socket on the bottom 2 bolt's it's a 9in.
In Australia, the Nodular Iron Centre was fitted to the GT-HO, not the GT. Good pick up though, not many people know about the Nodualr Iron Centre.
From memory, the Nodual Iron one had two vertical ribs, where the standard one only had one vertical rib.