I added a 7-pin plug into the bed of my 2022 F350, which did not come with the fifth wheel prep or under bed mount. I used a kit from Hopkins, that plugged in at one of the unused plugs under the truck, driver's side, near the hitch, and routed up to the bed. I did it for a slide in truck camper, so I mounted it slightly forward of the wheel well on the driver's side, close to where my camper pigtail came out of the camper. IIRC the factory Ford fifth wheel plug mounts at the very rear of the bed side wall, driver's side.
The Hopkins kit I got was for the Ford aluminum body trucks, so it came with aluminum screws. I used a hole saw to cut the hole. Pretty easy, the aluminum cuts and drills easily. I didn't need to add any fuses or do anything under the hood or under the dash.
I don't have pics because I don't have that truck any more.