To the OP and everyone else who tried answering without thinking things through: 15psi at idle and 53psi at 00 rpm are very much in line with the old "10psi per thousand rpm" rule of thumb. Why change anything? Your question seems to be based in ignorance. The first responders should have gone there first. Another thing: bearing clearances. I didn't see any bearing clearances that were out of line with what's been suggested here lately.

If you must do anything, add a high volume pump, you can do that from the outside. No need to mess with the spring. No need to disassemble the engine and add a 1/2" pickup. Maybe that's worthwhile on Hemis running 7000rpm for hours, NASCAR 1960s style, but for a street engine it seems to be just another way to screw up a perfectly good block.

IF you have all the money in the world, eliminate the internal pickup and use an external pickup setup, but it is clearly not needed on an engine that just the way it sits has 53psi hot oil pressure at 5000 rpm.

I don't care what oil pump you run, I'd change the pump drive/distributor gear to one that doesn't have a sharp step between the shaft and the hex. That is a stress riser or concentrator. Just from the mechanical design alone it is wrong.

As to the other items that popped up, fluid dynamics is not intuitive. That's why I had to take it twice. The second time through it popped into focus. Then I spent 19 years designing pump systems.

R.