I just went through this exercise on my 2013 Forester 3051S E-450. Yes, Ford prewired your RV for a 7-pin trailer connection. Forest River adds to Fords wire harness above the fuel tank and runs it out to the hitch. I was told I could buy a factory brake controller (plugs in behind dash above radio) and Ford could reprogram the ECU for the factory controller to work. I took my RV to Ford for the reprogramming but they couldn't get the dash instrumentation cluster to display the setting of the controller. The cluster is not setup to use a factory controller, even after attempts to reprogram the ECU in the personality sector of the ECU. According to the trailer plug tester, we were getting power to the trailer brake connector on the rear hitch but there was no way to read the brake settings on the dash. This tells me the wire harness is wired correctly and all you need is a pigtail to interface your aftermarket controller to the stock brake controller behind the dash located above the radio.
To use the stock harness you'll need to add a couple fuses and relays in the fuse box located under the hood, on the driver's side. Next, you'll need an aftermarket brake controller and a pigtail to interface the controller to the factory harness.
Finally, you can slave in new wires from the controller to the trailer connector located on the hitch. I have a pretty factory brake controller in the dash (looks pretty but doesn't work) and a Prodigy II plugged into the factory harness in the dash using a pigtail interface cable. I don't recall the part number but you can google it online.
Choice is yours....
2016 Days Camping so Far: 24
2013 3051S Forester
2013 Elantra GT (Toad)
WashU EMBA "39