The tach wire at the bulkhead connector is in cavity M....center connector the bottom hole farthest from the bulkhead index pin. Gray with a black tracer. It goes to cavity 2 in the tach sender connector. Cavity 4 has a violet wire with white tracer coming from the wiper switch power supply. Cavity 3 is a yellow wire going to the tach. Cavity 1 is empty. Oh, and there is not wiring for the vacuum gauge....just a hose.