I have the Hotwire Auto Hotrod harness on my '68 with a 5.9 Magnum & OBDII ECU. I only had to hook up 4 wires to make it work. Oil pressure and water temperature don't hook up to my Hotwire harness. I also didn't have to use the starter solenoid wire on the harness. I left the original wiring for the starter. I love the set-up.