I know this thread is over a month old but what you have here is what we call a half a hard wire, meaning the wires you want stop under the front of the driver side door near the back of the front quarter panel. You crawl under there and look in that area (body mount should be in line with the location. There is a quick connect harness there with alot of wires in it. THe ones you want are only on the front side of that harness, you should have 3 wires there not going into the other side of the harness (easily identifiable by 12 guage wires) which will be your towing package wires for the 12+ hot wire, brake output wire, and the reverse wire. For some reason if you dont get the factory 7-pin harness installed when the truck is ordered dodge didn't feel the need to stub the wires in the back like the other brands of vehicles.
That is one downside to Dodge Rams that need a brake control for their trailers.