Should have said what car I have. 1940 Ford. Run a wire from the terminal on the generator to the base of the voltage regulator? Seems strange that the harness didn't do that. Thanks for the information.
40 Generator should not have the ground post. It was added years later. The terminal is the body of the generator. It will not be necessary to add a wire to the terminal. Make sure the front bracket is grounded to the intake manifold at the attachment screw and the body of the generator has the paint cleaned off at the attachment of the front bracket and as well as the rear cover.
Orig replacement wiring prior to like 1942 did not have a separate grnd for Generator .You can add a separate grnd wire as Ford did after these years. ...If your running a 12V system with an Alternator and the engine is properly Grnded the alt Which is unpainted will be grnded when Bolted on..