8 3/4 Posi

In case you are new to Chryslers, there were actually 3 different cases - the 741, 742 and 489 that came with not a posi but a Sure Grip - the correct Chrysler terminology. The Sure Grips were either the clutch or cone style. Good luck on your search!
Correct me if I'm wrong but any suregrip can go into any of the three housings. Unless you get a pre 64 unit.