Plan to install a set of gauges with a tachometer in a non-tachometer dash. Other gauges are also configured differ. My concern is the dash wiring harness. Are the wiring harnesses the same for Magnum with or without the tachometer? I expect to add wiring to the ignition system but I need to consult the wiring diagram to access the Tachometer. Thus the question will the replacement gauges work with the original harness?