One of the prongs fell off the truck side hook up of a friend's 1996 F250 SD.  The truck came from the factory with the trailer towing package.  I've had a lot of Fords over the years and if memory serves me correctly the wiring was already installed and the hook up simply plugs into the truck wiring back up under the bed of the truck.  I am not in close proximity to the truck so can not verify this myself but am hoping someone else can.  Also, does anyone know the best place to find a replacement plug?

On my SD Ford, the factory wiring is hard wired directly into the plug, with no other attach points. I changed the plug from the seven blade type to the seven pin tractor trailer (rare) type. I am always able to purchase my plugs from a nearby RV dealership. Walmart and Sears usually inventory some of the more common types.

Gard