Check the plumbing to the
oil filters.
Many times I have read where the flow was backwards through the filters - an easy mistake to make by an expert.
Are the lines and fittings big enough?
Short elbow kill flow.
Many
oil pressure problems are in the external plumbing.
Try putting a T in the line where the
oil is comming out of the block and put a gauge on it there. See what the oil pressure is there before planning your next move.