And you would be correct, the grey wire on top IS for my oil sender. The tach wire is in the opposite (bottom) corner of the same connector. My bad, I didn't trace it out carefully enough. My '73 has a dimple where yours has a hole. But my car didn't come with a rallye dash, I added it and harness,etc, from a '74 donor. Now here's the other weird part, my 1973 wiring schematic shows the wire in the connector, but my 1974 (same year as my wiring)FSM shows the wire routed off by itself.