X 2 with matt. sounds like a battery on its way out.
Allowable parasitic draw for your 83 pontiac should be 30 -50 milliamps.
anything more than that and I would be looking at the underhood light , to check that it isnt allways on, or the GLOVEBOX light as well. Also GM factory radios of that era, were know to have draw issues with the memory circuitry,and it could be intermittent.