If you have a dual field unplug 1wire connector and ground the terminal to the alternator case.
Doesn't matter which field wire.
This by passes the regulator giving full voltage.
I believe Square back are rated at 74 amps and yes mid-late 70's 80's.
If you are going to ground one, it MUST be the GREEN wire that you disconnect. The light blue is switched 12V TO THE field, and by disconnecting and grounding the opposite field terminal (the one where the green was) you are causing full power through the field. If you remove the blue, and then ground that field terminal, you are grounding "nothing."