Is it time to replace my Oil Pump

Hello all, I have a question regarding my oil pump. When I first start my car (65 Polara with a 361ci auto) cold the oil pressure on the gauge is right at 40#s. After it warms up to180 degrees at an idle it drops to about 20#s, when I put it in gear it drops to about 12#Oil is clean and the car does not leak or smoke, Any help would be appreciated,, Thanks Dave (Catfish65)
Author: Catfish-65