Just a thought. If the sender is an oe type. Disconnect the guage and measure the resistance from sender to ground while the engine is running. 10 to 70 ohms should be about the range with about 23 ohms being mid guage (35-45 psi) 10 ohms would be very high like 80 psi and 70 ohms would be low like 0 to10 psi .
This is based on 0 to 80 stock 60s mopar oil guage and my memory and logic. ALL of which could be wrong. ;-)