I have to agree with your assessment to your next step to follow what Art says to do. I was short with you in circling those rabbit holes as well.
I don't work anymore but I had an appointment, to eat a $3.00 lunch at the senior center! (:) if that counts!
It gets me out of the house/shop for about as much social life as I can handle at one time? (:-)

Art mentioned spring contacts on the regulator housings. They fit up inside the alternator might be a problem let alone the rotors slip rings like Art noted.

The rings should feel relatively smooth when rubbing you finger or a finger nail, turned up side down, because the hole in fairly small. You can use a sharp lead pencil point across them individually to detect excessive grooving from arcing. Just drag or push the pencil with out any pressure.
Sort of like vinyl record playing needle affect.

You should not feel grooves with your finger, any great depth or sharp edges, on the outer edges of the rings. The height of each ring, relation to one or the other should be worn the same.
If not it could mean they are worn through as the base metal for them its not very thick. Those rings are replaceable if you are into rebuilding them.,
I trust my work over an unknown rebuilder. P-n-P have lots to trade-around-with!

I studying the the idea of trying that for fun, once I "lock on" to supplier. Looks like it can cost about $3.00 to replace them since I can turn that area in a lathe. Just have to not eat and talk that day!
(:-)

Phil