All Mustang IIs had 8" rear-ends, with gears ranging from 2.79:1 all the way up to 3.55 to one depending on year and options. In various years Posi-Lock was available on 3.00, 3.40, and 3.55 rear gear cars.
the small powered Mustang II's didn't get an 8" til 77.78.when it got a 302.