14 GA or 16 GA Fusible Link?

dibbons said
According to page 8-109 of the Plymouth 1965 Service Technical Manual the hot wire from the alternator to the bulk head connector is labeled R6, is black, and is 12 gauge.

However, I recently installed a new under-hood wiring harness I purchased online and it's hard to tell what gauge wire was used in that spot (the wire is black anyway). The other factor is: I am sure the installed alternator is not the factory installed alternator and may now have an amp output greater than the original factory rating. So now it's going back to a kind of guessing game.

View attachment 1715905140

As far the '65 fusible link, it doesn't matter that much what the alternator 'rating' is.
The main job of the fusible link is to protect the wires.
Chrysler used a 16 gage fusible link to protect the 12 gage wires.
It's placed in the battery line so as to protect stuff from battery grounding.
There's no link in the alternator output or hot wire as you call it.