Mike you can not hook the wire for starter at key switch to coil because it will back feed after it starts through the run terminal and start cranking the truck when it is running. You could get the correct switch from the dealer and install. To do what you want to do you could add wire at s post at starter but you would have to install a diode in line from s post to coil to stop it from back feeding when running. You could just take that wire out of the circuit and just wire to ballast and see if it starts good if so don't worry about it.hope l was of help.