As I recall there is a plug on the back of your small block, behind the drivers side head for the oil pressure. You get a new oil gauge line kit and install it at gauge end and engine end. Maybe it was next to the oil filter boss?
Cutting oil pressure line -
http://67-72chevytrucks.com/vboard/s...d.php?t=705484
Location of oil block connection -
http://67-72chevytrucks.com/vboard/s...42&postcount=5
Is that what you were asking?