Couple things to consider. A fresh engine with stock clearances and a 60 PSI pump should not make 50 PSI at idle speed. If the oil is 20W-50, that is too heavy IMO. I would change to 10W-30 and re-check the pressure. If you changed your oil pump around by switching relief ball sizes, shimming the relief spring and other things, I don't know what pressure the ball pushes off the seat at now for maximum pressure. I think people say on here 70 PSI with those. I kinda go with what has worked for me the last 50 years. I use a stock M54DS for most street builds. And a M54F for high performance builds. Never had an issue. I do install the thick plate on the 80 lb. pump. The ball and spring limit the maximum pressure to the flow rate it can pass, nothing more. In other words, it will try to limit a 60 lb. pump to 60 psi unless the ball, seat, passage can't bypass enough of that 50Wt goo and then pressure will go higher. I would verify your actual pressure with a mechanical gauge as well.
My personal street car with 10W-30 oil and a M54F pump starts and runs at 110-120 PSI cold for 1-2 minutes. Then drops to around 50 PSI during warm-up. Once the thermostat is open and up to operating temperature, it runs around 20 PSI, hot idle, 50 PSI at 3000 cruise, 78-82 PSI @ 6000 RPM on the dyno. Melling stock Pontiac pumps do a very good job of regulating pressure in stock form. IMO.
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