4 This is the neutral safety and back-up light switch, which gets a multiplex four-pin plug. Because Ford has discontinued this wiring connector, you will have to find it aftermarket. Ron Francis Wiring (www.ronfranciswiring.com; 800/292-1940) sells a new pigtail under PN PG-057 or you can find a used one. Wiring is simple—at the far left and going clockwise the first pair of terminals are neurtal safety and the second pair are for backup lights. You can buy the plug or use female bullet terminals to your Mustang's harness.