Just a guess. Need to use a multi-meter, and see if the two black wires are connected, which would make sense. If they are the same...past the positive battery connect, the red and black leads that feed to the starter, red to the main lug. Black wire to the solenoid. The other (forked terminal) end of the black wire to the square center terminal on the starter relay. The red ring terminal should go to the main (feed) lug on the relay, that supplies power into the car.
At least from the different diagrams I've been looking at, that's how it's wired up. Where did you get that cable from? Looks like one I could use on my mess.
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If I'm wrong on the power feed to the dash, feel free to straighten my act up. Still wiring mine up, and getting my head around that one thing, since you would think power would be 'on' all the time to the dash. But, that's the way it shows.
Just be SURE those two black wires are the same.
