Nothing wrong with reviving an old post if it's relevant to your problem, There's always new people to read and learn from it.
Using a one-wire alternator is as simple as it gets. You should be charging with it wired like you have it now except the battery gauge won't work like it's wired, with the output wired directly to the battery plus post.
In order to correct the wiring you will have to know how it was wired to begin with. The central point in the harness is a junction of the wires that feed the battery, the cab, and the external regulator, all from the alternator. I have a diagram of the stock wiring with the HEI distributor wired. It should help you see how to wire yours.
Follow the red wires to the junction in the bottom center of the diagram and you'll see where they originate.
The one wire alternator will eliminate all the wires to the alternator and the regulator and you can just run the single wire off the alternator stud, not 2 gauge but maybe 12 gauge I'm thinking, to the junction of all the red wires in the center of the diagram.