The factory gauges used copper line and a port to the engine block. I even bought the copper tubing and correct fittings from lockdoc, but decided to change mine to an oil gauge with a sending unit and modified the face of the gauge to have an OEM faceplate. I just didn't want to run the tubing and hope I don't get a leak at the gauge. Just always scared me.
http://67-72chevytrucks.com/vboard/s...d.php?t=613238