Need help with wiring one wire alternator

Well, "what have you changed?" Is this an otherwise stock harness? The original key switch source is from the black ammeter wire up under the dash. If you have repaired/ replaced terminals on the big red and big black ammeter wires, and left the rest "in place" that will take care of it.

This simplified power distro from the MAD article shows basic original power distro

Catalog

amp-ga18.jpg

"Everything" except the main starter power pretty much comes off the "welded splice" which is / was a few inches from the ammeter on the black wire.

Be sure to put some sort of protection in the new charge wire, fuse link/ fuse/ breaker