charging system trouble

If it had 2 wires on the back (a 2 wire field) then if the control line for that type from the VR got grounded, the alternator would go to full tilt output. But you only have a 1 wire field connection so that is not it. Normal connections for your year car.

Is your voltage regulator a squarish looking thing with screw terminals, or a flat brick with a molded connector? Should be the former; just makin' sure no one snuck something else in there in the past.