416 low oil pressure at idle

Hate to bring up old post couldn't find anything else close ,
I have run 3 different oil grades , replace bearing ,rods and mains twice, I am having same issues with low oil pressure(10-20) at Idle (oil pressure gauge looks like a tach) and goes to 60 psi above 3000 ,I have tried big and small wix and napa gold oil filters, I really cant afford to keep tearing down engine , I am a average working man, I do have solid roller cam bullet but no idea what brand lifters , any and all Help would be helpfull