66 Valiant Starting Aggravation

I have to assume you checked your battery voltage while running just to be sure the alternator is working properly. If so I'd pull the negative battery cable and put an ammeter in line with it to check current draw, it should be zero amps. Something is probably staying on and drawing current. That something could be a radio, glove box bulb etc. If you are pulling current start pulling fuses to find what circuit the draw is on. It should not be too hard to track down. You may also check the car at night and look for any lights still on. Good luck.