'71 Duster 340 Battery getting overcharged

I would not bet the VR is the trouble. "Start over" now with troubleshooting

1....Very first thing to do is make sure the VR acually has control of the field, IE not a field wiring problem OR one brush grounded. Disconnect the VR plug, run the car and see if it charges. It should NOT

2....Next look at voltage drop, both the supply to the VR and the ground. With key on but engine stopped, measure voltage between the blue field connection and battery +. Do this with everything hooked up "normal" that is, "back probe" the terminal. You are hoping for a very low reading, below .3V (---3/10 of one volt). If you read more, you have voltage drop in the path from the battery to the VR

3....Check ground. This is going to have to be somewhat interesting because it's overcharging. Start and run the engine, and check first with all loads off, and again with lights, heater, etc turned on. Get the engine up to some RPM around 14-15V on the battery. Then take your meter as before.......

Stab one probe into the top of the battery NEG post, and the remaining probe into the VR mounting flange. You are hoping, again, for a very low reading, zero is perfect. This shows ground side voltage drop. More than a tenth or two, you need to improve the grounding from battery--engine--body