Classic/Antique Car Repair: electrical, negative battery cable, radiator core

Question
I have a 1968 cutlass that has an intermittent electrical condition. when I turn the lights on, it killed the power completely once. another time I experienced a dimming condition also with the lights on,applying the brake and using the turn signal. Is this a sign of a bad voltage regulator, or possibly a bad ground?
I took a reading at the alternator and got 14 volts with the car running and the terminals are clean on the battery.

Answer
Dave, right away my mind clicks right over to the ground side of the electrical system. On that car there was a pig tail from the negative battery cable that ran to the body. The main ground ran to the engine near the alternator bracket and the pig tail to the body radiator core support. Make sure that there is a ground connection to both the engine and the body.
Brad