I don't see why you couldn't just run 12v from your new dash switch to one end of the resistor and go from the other end of the resistor to the coil. Considering it would be the only draw it should give you 9v or so at the coil and that should be enough to start the truck. After all that's the power it uses when you are in the run circuit of the ignition switch normally. If that wouldn't work some one will correct me.