Clarification on 70+ alternator VR on 68 cuda

You need to add one wire

You can take the old VR wires yes and add them direct to the new one, blue to the IGN terminal, and green to the field terminal.

Hook the new alternator up just like the one..............!!!BUT WAIT!!!1

You have one more field terminal..........Run a wire from that new field terminal up and splice to the blue IGN terminal

While you are at this, check for voltage drop in the harness, which will cause OVER charging (over voltage) at the battery

Turn the key to "run" with the engine off. Put one multimeter probe on the battery POS post and the other on your blue IGN terminal. You are hoping for a very low reading, the lower the better. ANY drop there ADDS to the charging voltage. Over about .3V (3/10 of one volt) is getting to be "a bit much."

Causes are drop in the harness. The blue wire terminals passing through the bulkhead, the ignition switch connector terminals, and the contacts in the switch itself.