I have a 431 and while Driving at 2500 rpm my oil pressure holds at 62lbs. When I luanch from a red light it drops to 0 Then comes back up after 20 seconds or so.
Your first priority should be getting a good HP oil pan.
And when you R&R the old pan ... I would check a couple of bearings. Letting a motor run(especially under WOT) and having to wait for the oil-pressure to come-back to normal COULD NOT have done the bearings any good.
