Help with no power??

I don't intend to "sound easy" and parts of this circuit are not "easy" to access but follow the path. It is only two wires,

If you are sure you have power at the INTERIOR of the bulkhead on the RED wire, the next stop is the ammeter.

From the ammeter (BLACK) it goes a few inches to the welded splice. From there power branches off to headlights, ignition switch, and fuse panel hot buss. If ANY of those work, but not all of them, the welded splice has likely failed.

DOES ANYTHING, anything at all work?

Look at the path in that diagram. Put your meter on the big black wire output terminal of the alternator. Any power there? Now turn on the headlights. Does that power go away? You have a bad connection in that path. Just follow it like a road. No difference.