Correct, black wire grounds case to the chassis. What I don't get is what is different about the old alternator (left picture) and new 70's model. They appear identical.
Please re-read my post. You must remove BOTH field wires from the alternator and check continuity from the field to ground. It should be OPEN. If this is so all you need do is hook up the new regulator.
One field terminal goes to VR via green
VR must be grounded
VR gets switched 12V
VR has the green connected to one field
Other alternator field terminal goes to switched 12V "ignition run"
The old system, the VR sent power TO the alternator field. More power to the field= more output
The new system controls the "ground" via the green wire. One field terminal gets 12V instead of ground (old) and the VR controls "the amount of ground" so to speak
