The usual place to mount the 7-pin trailer plug is right next to the receiver, but this leaves it susceptible to damage in trails. The alternative is to mount it IN the bumper, but the Expedition One bumper follows the frame contours pretty well. I only found one place to mount it, and even then had to do a little 'body panel massaging' to make it fit. :-)

Here's the location:



You need to use a length of steel and a sledgehammer to push back the body panel behind the hole about 1/8" or so...



Here's a shot underneath as I was checking clearance. I still needed to make a little more room. :-)



The socket is at a slight downward angle, so I drilled a small hole at the bottom, in case any water gets in, and stuffed some dielectric grease on the connectors.

js.