If I understand correctly, you swapped the points system for the pamco, and also simplified the wiring. I assume your bike is not charging. but you believe the rotor is good and also the brushes measure at least 3/8". You suspect problems with the stator and/or regulator and rectifier. You also know the charging system from the '81 works properly.
If that is the case, there shouldn't be any reason I can think of, not to switch the stator, regulator/rectifier from the '81, leaving the rotor as is. Remove the pickup from the stator assembly, you won't need it.