Burned bulk head connection

Looks like a '69 from what I can see of the diagram. Yes?

'69 shows only 12 gage wires used on the main feeds, except battery to starter relay.
You've got a few choices on the alternator feed. Not seeing any advantage to drilling through the bulkhead unless you want to keep the routing looking very stock. Some sort of heavy connector with lots of surface contact area. Maybe a molex or similar bullet connector.
Other choice is route new wire through a grommet with a ring terminal to go over the ammeter stud. That's what Nacho did. And he left the original wire in place. In your case you'ld have to make new one and ther terminals may not hold well in the damaged connector.

Or run one or two wires through a grommet. One to the ammeter, the other connect to the original alternator feed inside.
If two wires, I'd make them both 12 gage. If just one, might as well go up to 10 gage.

Posted recently by a member parting out a defroster grid equiped '73
These are the connectors Chrysler used.
One wire direct from the alternator output, the other from the battery.
View attachment 1715472758
Ring terminals went to the ammeter.
View attachment 1715472757