oil pressure goes from 65 psi to 30

Could you be sucking the oil pan dry?

Or, look behind the camshaft thrust plate. There should be two oil galley plugs in those oil galleys. Some people think that they are not necessary, I had those two cause a problem on an engine that I rebuilt many years ago. Once I installed those plugs, my low oil pressure was cured. They wouldn't leak the pressure all of the time....

Here are the two plugs that I'm talking about:

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