the oil pressure gauge should go into the hole on the passenger side a plug goes into the driver side. Might not matter though witch way it goes. The oil gauge has a big canister on it the oil light has a small sending unit. I am guessing that 72 came out of a c-body and is set up for hot and cold lights in the dash. you might have two temp gauge senders and no oil gauge sender. You might want to go with after market manual gauges as long as you in there.