One wire alternator nonsense

As is typical, this mess is going backwards in a hurry.

The black wire coming off the alternator was pretty toasty at the bulkhead. In the cab, it’s bare all the way to the welded splice. So what next???

Do I just find a clean piece of wire just before the splice and make a whole new wire?? Also, trying to follow the Mad Electrical plan and it seems to me that black wire is the wire that you remove and replace.

Disclaimer: I’m am electric stupid. I suspect my car will be in the same shape, so this Duster is a test run before I unscrew my car.

What’s my next move??? I know replacing the black wire for starters. Then what???