Hey guys i was wondering if anyone knows which wire in the truck and where is it? to connect my parking brake wire to from my pioneer head unit?

 

Down by the foot well there is a little parking brake pedal. Look right above the pedal there should be a cable which engages the parking brake, and a wire... the wire it what you want...

What brand and model # radio are you installing? as some of them you can simply run to ground to bypass that feature...