Im not familiar with the Ford switch internal wiring at all, but the components Ive had to swap polarity on at work have been like this:
Open up the casing. There should be a diode that connects to the casing and the ground terminal. There should also be a small piece of wire connected to the positive terminal and the rest of the switch. You will want to unsolder both the diode and the wire, switch places, and then resolder them back together. Take note of the diode direction to as it only works one way.