How do you wire the factory tachometer 1972 Chevelle?

To wire the factory tachometer in a 1972 Chevelle, connect the tachometer's power wire (often marked as "12V" or "IGN") to a switched ignition source for power. Next, connect the signal wire (usually a green wire) to the negative terminal of the ignition coil, which provides the RPM signal. Finally, attach the ground wire to a suitable chassis ground. Make sure to consult the vehicle's wiring diagram for specific connections if needed.