52 F1 turn signals

[Doug-F1]

The fifty two F1 I have came to me with a Autolamp 9000 self canceling turn signals. It has three wires coming out of the switch a green a red and a yellow. The red goes to the flasher the other two don't go anywhere,there cut off, there's a black coming out of the flasher block and a spot for a third wire that isn't there. My question is was this turn signal unit designed to run only two lights and not four? When I got the truck many years ago the unit was attached to the steering column but the wires were cut so I have no idea what the original setup was.