I don't know how this works specifically on the F-body harnesses, but typically the purple wire goes directly to the starter solenoid. You'll want this run though a relay to a +12v supply. The relay coil should be hooked up to the crank line from your ignition switch through the neutral start switch on the side of the trans. There should be a yellow wire going into the neutral start switch from the ignition switch and a purple wire coming out going to the starter relay coil.