87 Rear Tail light issues -- Help

[remist17]

I purchased some new rear taillights for my 87 Chevy Stepside. The wiring must be all wrong since the brake light is now the reverse light and the running lights are not really bright.

I have three wires coming out of the bed... yellow, green and brown.
The wires from the lights (purchased at Classicparts.com) Ones Brown, white, and red.

Two are together and one is seperate. If any one can help me out with what wires go to what I would appreciate. I am looking for the wire id on the truck and I will figure out the lights.

Thanks