2002 Tundra trailer wiring questions

[lilchopshop]

I have a 2002 Tundra SR5. Currently I have a T-One harness that plugs into the factory connector under the right rear of the bed and gives me a flat 4 connector. I want to install a 7-pole RV receptacle in place of the flat 4. My basic question is: what do I need to do?

I see that there are 9 wires going into the factory connector, but my T-One harness only uses 6 of them. What are the other 3 wires? I am also installing a brake controller. It is an old one with no connector anymore. Is there a connector somewhere in my dash that I should connect this to, or do I need to run new wires up to the battery and back to the hitch?

Any help is appreciated.