The best way is to mount an additional 7 pin RV plug into the box of your truck behind the wheel well, this also allows you to hook your RV in summer. It is out of the way and not dangling outside or allowing corrosion of the factory bumper plug. It also allows for an additional hot wire for under deck lighting or loading ramp lights.
Marathons use the above pictured two pole connectors which are held in place by plastic hose wedged between the extrusions, these plugs corrode off regularly in salt conditions, dielectric grease all of these if you keep, I remove them all and wire in solid with solder, shrink sleeve and add plastic loom. My center marker light was also corroded off at the backside of base and needed to be replaced over summer.
The seven pin harness assembly can be bought at Canadian Tire in the RV or Trailer section and is plug a play also pictured earlier in thread
Marathons use the above pictured two pole connectors which are held in place by plastic hose wedged between the extrusions, these plugs corrode off regularly in salt conditions, dielectric grease all of these if you keep, I remove them all and wire in solid with solder, shrink sleeve and add plastic loom. My center marker light was also corroded off at the backside of base and needed to be replaced over summer.
The seven pin harness assembly can be bought at Canadian Tire in the RV or Trailer section and is plug a play also pictured earlier in thread