Need HELP with Alternator Wiring!!

[Gs835.8Stang]

I hope someone out there can help me. I am attempting to hook up the alternator on my project 83'. I am putting the alternator out of the 85' bronco donor vehicle into it. All of the connnections appear to be similar.
I know where to hook up the terminal marked "BAT" and "FLD" as they appear to match up to the harness for the 83'. Another terminal is marked "GRD" which I assume to be ground. The 83' does not use this terminal, on the 85, it appeared to be hooked up.

The one I need help with the most is marked "STA" I have no idea what this is or where it should be hooked up to. Should it have 12V constant power? 12V Key on power?

If anyone out there can help, I would greatly appreceiate it.
Thanks in advance.