You can use the plug at the bumper with an extension cord. No need to drill large holes in the truck bed. Ford truck bed is a double wall and the cord runs inside the walls. You may need to undo one end connector to pass thru the hole in the truck bed wall and the bracket. Cable is color-coded to match the marked connectors. Easy to reassemble.
1 male connector
1 female connector
1 8' 7 conductor cable
1 mounting plate
About $30.00 total
You can buy an extension for about $25.00 terminated with the right connector on each end. You may need to remove one end for lacing the wire.
Check MY PICTURES below. I ran my plug from under the truck and up through the driver side rear taillight and into the bed.
Take a look. It worked out real well.
Be safe. Bigdon68
2008 F350 CC 2WD LB 6.4 Lariat Auto SRW, Retrax, AirSafe Hitch, Train Horns, On-Board air, RideRites, Aux Tank, 19.5 Michelins
2016 Mobile Suites 38RSSA, induction cooktop, solar, (4) 6 volt, full body paint, 17.5" Tires,residential frig., more