76 breaks problem

something is certainly afoot. obviously getting a 12" 6 bolt drum when that's not only wrong for the application but wrong in the box is a whole issue.

i'd start with 100% confirming what you have cooking. a lot can change in 50 years. verify your rear end, bolt pattern spacing and diameter of the studs, and the same on the front. if you're not sure pics help and the train spotters here can id damn near anything.

the centering hub for the axle looks oddly tall to me, but maybe that's just how 7.25's are