Something is obviosly pulling current. Or not allowing current to flow to the batt.

Im thinking its just a wiring issue. A car will run with just the batt, especially if its carbed. I drove from Taco bell in front of spotsy mall all the way to stafford KG line, then it died.

You might want to check all your wiring comming off the alt.

Turns out on my alt, the wire had broken and that was the reason it wasnt charging. Happens when you have an original car from 71.

I doubt you need an HO alt, unless you run your air suspension everytime you hope in the truck.

Check the alternator wiriing, does it have an internal or external voltage regulator?

Pull fuses on all uneeded accesories and be prepared to spend time hunting it down.