'66 Valiant Weirdness

Not sure if this was asked and answered but I had a similar weird charging system with my 66 Valiant. I had replaced the alt and VR and things got very wacky.
Turns out I had gotten a "newer" square back alternator and it had dual "fields". I had connected one and left the other not used. I needed to ground the one that was not used.
Just my $0.02.
Good luck!