I just hooked up my OER tach the way you guys mentioned but it did not work. My car would not start. I peeled the factory tape off of the OER tach harness and noticed that all the grey wires are hooked together and go to the tach lights. The black with pink stripe wire goes only to the tach. Soooo I hooked up the black with pink stripe to HEI tach terminal, black to ground and grey to power/ignition on. This works perfect. The grey wire must be hooked to ignition power or the tach won't work. If you want the lights in the tach to work only with lights on, you would have to seperate the grey wires in the tach harness. The grey wire that goes into the tach gauge, ( must have tach apart to see this) must still go to ignition power and the grey wires that go to the tach bulbs would than go to lights on power. Most after market tachs have four wires which make it easy to have the tach light hooked to a lights on power wire. Just my two cents...well, if you add up all the bills, tach, hood, scoops hood emblems, paint ect its more like " my $1000 ". Hope this helps.