speedo has a sending unit which screws on the tranny and sends a signal thru wires to the gauge. water sends a signal thru a wire from the temp sending unit in the manifold. Oil the same as water. Volts wires to the sytem. Tach wires to the msd or coil and sends a signal thru a wire. Fuel sends a signal from the sending unit in the tank to the gauge. Hope this helps.
