Is it possible to keep old style electronic VR with a dual field alternator?

KitCarlson said
The electronic regulators were low side switched because in the early 70's NPN transistors were more reliable and cost much less than PNP, necessary for hign side switching. The old style electronic units became available in the late 80s.

Thanks Kit!

For fun I was trying to figure out the basic electronic VR circuit.
Usually the master tech booklets are pretty good, but in this case Tech and the illustrator seem to have goofed.
The 1970 Alternator & Regulator (Session 269) from the Master Technician's Service Conference
There is a photo of the guts, but this is over my head. I can follow but not reverse engineer this. There's too many things they left out of the schematic.
So got this far and stopped.