With the small bolt pattern on the 67 Cuda wheels you're stuck with either a 7¼ or 8.75 rear end. If you want to convert to the 4½ inch bolt pattern, the 7.25, 8.25, and 8.75 rears are out there. The 8.75s are the strongest, but also the most expensive.
If you're not opposed to mixed breeds, the Ford Grenada, Mercury Monarch, and Lincoln Versailles of the mid 70s had 8.8 inch rear ends, 4.5 inch bolt patterns, and have the same spring spacing as the A-body. In the case of the Versailles, you also would get disk brakes. The 8.8 is stout and well supported in the aftermarket.
