An f or fie indicates the field terminal.
Old ford voltage regulator wiring.
One way to wire a 3g alternator in place of the old 1g setup is to simply splice the old external regulator s i and a terminal wires into the corresponding wires from a 3g connector pigtail.
Connect the field wire field coil wire to the field terminal on the regulator.
Connect the generator or alternator wire to the regulator.