[CREWZIN]

Welcome to the forum. Even with your older car without a computer, it's extremely hard and time consuming to find your electrical problem especially if it's intermittent. Somebody that's really good with electrics should be able to trace down the cause of your drained battery.

You can start by pulling any fuses to any accessories that you have and don't need to drive the car (fog lights, stereo, rear wiper etc.). Also, are they checking your charging system when they put the new alternator and battery in. Their "new" might be "rebuilt" and not working/charging properly.

Do you have a multi-meter that you can hook up to the battery when you park so you can keep checking it for a drain?