get the Bargman 7pin extension like
this from Amazon. I just installed one on my 2012 F350. comes with the screws and a spacer if the back space is too tight.
I had a little trouble getting the harness connector to seat, but Cequent (makes Bargman) suggested that the gasket in the ford harness was dry, and a little dielectric grease or vaseline on the inside of their connector would help.. It did.
install was easy, cut the hole, slide the connectors and harness thru the hole, position the new 7pin connector, install the provided screws, unclip the 7 pin connector at the bumper, plug one side into the ford harness, one side into the connector.. wire tie the spare length up out of the way.. , push the ford 7pin back into the bumper bracket, done.