Stop in for a cup of coffee

Well that's about the limit of knowledge and library for Delco systems.
I'm don't know if there was a simpler or electronic version of the regulator before GM switched to the self - exciting internal regulators.

It looks like the 5 terminal regulator may not need the indicator lamp, but the other versions might. When I see a parallel resistor, that makes me think its a back up in case the lamp burns out.