76 Duster

It will be either a 7.25 or 8.25 rear. If I'm not mistaken by 76 the 8.25 was the only factory option (please correct me if I'm wrong on that guys).

If you two and picture of the rear end cover, we can tell you what/which rear you have. If it's a 7.25, start looking for an a body 8.25 now.