[truckin 79]

I would check out the starter solenoid could be drawing a lot of amps. I have always used the cheapest battery on the 79 Trans Am and Truck with no problems in cranking, CCA is a selling ploy unless you live in Alaska or have a high compression engine. Is there a Autozone or Advance Auto near you? They can check the entire charging system while on the car. Be careful if the starter solenoid is bad you can burn up a good battery quickly, volts and amps are 2 different animals.