Since you have stated that you do have the later model trans, and 3 wire switch, and wiring in this 67... all you need to do is find a odd shaped 2 wire connector ( it should be somewhere between brake pedal and firewall, left of steering column, its there whether plugged directly into a column mounted switch or instead has/had a console extension harness plugged into it ) with a purple and a white. Connect those 2 later model wires that someone has already brought into the cab for you.
