DoctorDiff sells a bearing sleeve that allows you to run the larger 73+ bearing and convert to the 73+ rotor while still using the early spindles.
'70 - '72 Mopar B/E-Body Disc Brake Spindle Sleaves
I’m not sure if it’s still a available, it’s been some years since I looked into it, but there was a reproduction rotor available for that application that was one piece. It was more expensive than the 73+ rotors, but not nearly as expensive as actual 2 piece rotor reproductions.
