I think the black wire in the picture is connected to the oil pressure idiot light sender.

There needs to be a ground wire connected to the alternator, a small red wire connected to D+ on the alternator and a larger red wire (B+) that goes to the battery. It won't work if either of these wires are not connected. As I recall the ground on the last one I looked at was connected between the back of the alt and the alt mount on the engine, but doesn't matter as long as it is there. Looks like some hack job repairs from the PO!

These wires go into the engine harness that goes under the front part of the engine. Dan