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This is for the alternator with the internal regulator. there should be a small red wire that comes out of the engine harness with the oil pressure gauge wire. It comes from the "amp" dash light. It plugs into the spade, and it is not a ground. From my understanding it provides the seed voltage to get the alternator started. The alternator should be grounded, usually by a short wire going from one of the nuts holding the alternator case together to a bolt on the alternator bracket. The only other wire is the big red one that runs from a nut on the back of the alternator to the starter motor (another red wire runs from the starter moter to the battery). You can identify the nut on the back of the alternator because it is insulated from the rest of the alternator with a non-conductive washer of some kind.
I can't remember the external reg setup, since I have not seen one for years.