Replacing the regulator harness on my 71 and have a question.
Is the wire marked in the picture simply a ground wire?
I assume it simply mounts where the regulator mounts to the inner fender.
My diagram isn't clear and I don't want to fry anything.
That's the Batt+ wire from the alternator. Since you have a three conductor voltage regulator plug, I assume you have the gauges dash. The wire *should* have been Black with Orange stripe, and it gets paired on the terminal block with the other Black w/Orange stripe coming out of the engine compartment harness. The heavy yellow will be on the battery side of the starter solenoid.
If you haven't already, you can download the 71 wiring diagram manual from the Wiki.