I drove a 65' chrysler 300 for years and it had charging issues the whole time. I replaced voltage regulator, ballast resistor, alternator, wires, made sure all the grounds were perfect sanded the firewall to bare metal used dielectric grease. Switched to a later 2 field wire version with modern regulator. Then switched it back, damn near lost my mind. My brother who was finishing his electric engineering degree comes to visit me. Looks at it for 5 min. He runs a length of 14 ga wire strips it with his teeth and runs it from the back(ground) of the voltage regulator to the negative battery post.... Charged great after that....