battery light Comes on and off.. Any idea what it might be

alt could have a short on and off.... but, Suggestion is check all cables and grounds. A cable terminal can have a bad connection between the cable and terminal, that you cant see, disconnect and do a continuity test, it should show little or no loss, and the battery ground where it bolts to block or frame . That randomness you describe leads me to think of cable connections

Since its an older car may can find a used Repair manual on auction site cheap, then look for procedures & step by step instructions. If testing the Alternator remove it to have it load tested instead of pulling the negative battery cable to avoid damage to electrical system. As said before check battery Cables & terminals need checked, if they are original May just be time to replace or if loose tighten and if corroded replace.