On my 440 with Crane Ductile Iron Rockers. my oil pressure was 50 PSI cold, and 15 PSI Hot at Idle...20/50 VR1 oil.

After buying a new set of New Comp Steel & Bushed roller rockers and shafts, I went from 80 PSI cold to 25 PSI hot at idle.

Almost all of my loss was due to loose fitting rockers.

Just another are to check.

Mark