[T3] Wiring for brake switch

[Roy Pitchlynn]

Changing from single circuit to dual circuit master cylinder. The car, 1964 Squareback, had a single prong brake switch, thus only one wire. We picked up a new switch today and the choice was 2 prong or 3 prong, but not single prong. So my question is, do we need a single prong switch or do we need to add a wire and where does that wire tie into?


Thanks in advance. 

Roy