"Lost years" Cougar needs help

[psychotic1]

I have an '82 XR7 with a 4.2L. I am having trouble with the battery. I had the battery tested, it's good. I also had the alternator tested, it's good too. I just replaced the voltage regulator. There is no draw off the battery, but it keeps going dead on me? I am at a loss for ideas. I am also wondering what is underneath the vinyl top. I want to get rid of it, but don't want to take it off and end up screwed. Any help would be greatly appreciated