Momoney43

Was hoping someone could walk me through the gauge swap over. I have a 73 Hurst with the idiot lights. Have the Rallye Gauge, but know that it is not just a simple plug and play. I know the sending units and such have to be swapped out, but someone once told me that you have to cut and swap some of the wires in the harness that plugs into the back of the gauge. Any help or comments on how to complete this would really be appreciated.