I had no luck googling that part number. Do you know if the regulator is mechanical or transitor type?
besides extra grounding reguloator, I think the altenator should need a good ground also. having the wires go to the same point on the chasis would be good. I would also look at the wiring providing the voltage to the regulator. It should be coming from the large cable to the starter terminal.
Do you have a test meter to see if there is AC volatage on top of the battery DV voltage.
also could you do a charging voltage test where you first measure just battery, then when at above idle, then with all loads on
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