I was reading Tom Condran's book (Performance Handling for Classic Mopars) and on Page 5 he writes:
I see that Layson's Restorations and the Paddock carry a unicast (combined hub & rotor) version of this rotor. Has anyone tried this B-Body rotor on their A-Body K-H disc brakes? Does anyone know which company manufactures this rotor for Layson's or who else carries this rotor?Regrettably, '65-72 rotors can not have the stud pattern re-sized to the large 4½" pattern common to other Mopars. There is no "meat" where the machinist would drill. And outside diameters of the hubs (which center wheels) match only small bolt-pattern wheels.
The bolt pattern can be up-sized only by swapping on rotors from a '66-69 B-Body, if you can find two of those rarities in good condition. These Bendix rotors - and not the calipers from that system - match A-Body knuckles and calipers as if they were built for them. They even share wheel bearings.