Hey, Gecko
You can't do any better than your Delco 12si 96 amp alternator ... that's not your problem.
Your headlights should not be causing a draw though -- something isn't right there -- double check all your wiring on your headlights; make sure you have a good clean and solid ground.
You might consider headlight relays ... see
This Another thing that comes to mind is *where* your gauge is reading your voltage (amps) from. Many people piggy back the third wire to the alternator to the back side of the alternator and that is NOT the way to properly read voltage. I ran that wire to a terminal block I installed on my firewall (under the hood) where I run power to everything (like my headlights) and THAT tells my gauge how much power I have, where it counts; an honest and true reading. See
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