Oil pressure with a warm engine is pretty much determined by bearing clearances and pump capacity; the external pressure regulator should be used to regulate the cold oil pressure which, if too high, can rupture the oil cooler core or oil filter, or both and if extreme can even blow out the bourdon tube in the oil pressure gauge. With a cold engine and whatever viscoity oil you intend to use, remove the acorn nut, loosen the lock nut, and with a large blade screwdriver set the pressure such that it does NOT EXCEED 60 lbs., assuming the internal condition of your engine allows that much pressure. A 34 Eight engine in good condition and so set should then deliver 15 lbs or more at a hot idle, and between 30 and 45 lbs at road speed. Anything significantly less than this indicates attention is required to the pump or bearings or both though the first thing I'd probably check if the engine hasn't been serviced recently is the pump intake screen which can be accessed by removing the cover plate which is adjacent to the oil drain plug screw.