Keep looking for the proper brake controller plug. Our 2001 F53 chassis had the plug under the dash and our 2013 has the same plug. I believe the same wiring harness is used on several models of truck chassis. The wires you've found are used on models with a built in brake controller.
Keep in mind the plug will probably not plug directly into your controller. Most after market controllers need a chassis specific jumper harness. The plug on 1 end matches the chassis socket and the plug on the other end matches the brake controller
Hikerdogs
2013 Winnebago Adventurer