Alternator Extra Wire Help

[BuffDrinkLots]

Hey all,
I’m sure this has been discussed thoroughly, but could not find what I needed.

My situation:
1972 C10, External Regulated Alternator (DL7133)

In pic 1 is the wiring from PO, it has a plug in black and yellow wire, and one wire at the Batt location.

In the others pics, is the new factory wiring harness, it has the plug in white and blue wires, red Batt wire and an extra wire that I think is brown or black that the alternator never had previously. I am assuming it’s a ground? Where does it go? I was just gonna bolt it either to the frame or put it with the batt and put the rubber boot over both. I don’t see anywhere on the alternator that says “ground”. Any help would be awesome! Thank you.