Well, first, they're not worthless. Plenty of people have run them successfully.
@Charrlie_S being one. I've had the original one in my 64 since I bought it in 2019 and been driving it everywhere and it's fine. Slant six car, but lots of people have had them behind V8s and they lasted. Lots of them have broken, too.
Now that that's outta the way, another 7 1/4 of course, an 8 1/4 from a later A body or the 8 3/4 will all bolt in. The 8 1/4 will have the larger 4.5" bolt pattern wheels, so that issue will need to be addressed. Although, I believe the drive shaft is a direct swap.
The 8 3/4 has two issues. First, everybody thinks they're gold plated. Good luck finding one for under a grand. Secondly, if you do find a good deal, the drive shaft will need to be shortened. That's no huge deal.
Those are essentially your "bolt in" options with other rear ends that share the same spring perch width and same overall length.
Other than those, you would need to modify something like a Ford 8.8 or Ford 9" or perhaps a B body rear end.
