First in my opinion your oil pressure is fine and good to go. I have seen newly rebuilt SBC engines with almost 0 oil pressure at idle after warmed up and only 30 psi under power or at cruise speed. They still ran fine. They were set up with the clearances on the high end for drag racing.
What you must have is circulation.
Very high oil pressure (i.e. 80-90 PSI) can actually be harmful to the engine as the oil is forced thru the journal area resulting in the shaft actually touching the bearing surface instead of floating on a film of oil.
Some reasons for low oil pressure: Excessive clearance between the cover plate and the gears in the oil pump body, main bearing clearances acceptable but on the high end, excessive clearances between the cam bearing journals and the cam bearings, internal leaks in the oil passages, missing oil passage plugs. Wrong viscosity oil can contribute. Your engine and the factory clearances were designed for straight 30 wt oil. Unless you have tightened up the clearances, you may have difficulty maintaining oil pressure at a level you think it should be, if you run multi viscosity oil.
Hope this info is helpful to you.