Fusible Link
If one end of the link terminated inside the bulkhead, the best route is to buy a connector already made up.
There should be a couple suppliers.

Looking at the '67 Plymouth FSM, the wire labled A1C-16DBL is the fusible link.
They show it going from the battery connection on the starter relay to the bulkhead connector.
Maybe that's so, or there may be another connector in between. That's the way my '67 Barracuda is done.
Another reason I'm guessing the B-bod diagram is missing a connector is that the battery feed wire sequence jumps from A1A to A1C. So its probably an oversight in drawing. But you will know when you look at your car.

Alternator Insulator
If its just a wire terminal issue, then the protective cover above will work.
Take an ohmeter and measure for continuity between the output stud (BATT) and the alternator's case. If there is any continuity, then its internal.
I'll post some pictures of that in another post.