FABO nation - thanks for chiming in. I just spoke to Mancini Racing about their MBM front disc brake conversion kit, big bolt pattern, for 62-72 A-body Mopars, P/N MBMDBK6272A-45. It's an 11" rotor bolt-on drum-to-disc conversion and the description says "Fits most 14" original rims. DOES NOT FIT: Cragar Steel, Year One Rally or original small 9" Drum braking system rims".
Mancini's tech line verified that their kit works with original Mopar rallye rims, is big bolt pattern (nice!), and has no issues between their rotor hub registration and original rallye wheel center bore. They did mention that their kit utilizes GM-style calipers and if anything on some early model A-bodies a tiny bit of grinding on the caliper may be needed (similar caliper grinding was detailed in a 3/1/2019 Hot Rod mag article on converting a '66 Dart GT to front disc brakes:
https://www.hotrod.com/how-to/convert-mopar-body-front-disc-brakes/
The Mancini kit appears to fit what I am looking for: (a) non-drilled or slotted rotors for quieter braking, (b) big bolt pattern, and (c) fits original rallye wheels with no hub/center bore issues.
If anyone sees any issues that I might have overlooked, please chime in. Thanks, Dave