I don't think HP has anything to do with pressure requirements. 50 years ago Cummins dropped their oil pressure from 60 to 30 on their 855 cu in engines to gain a little extra HP and fuel economy. It took some getting used to seeing oil pressure drop to 20 on a hard pull, but we got used to it. Idling at around 10 psi was common. After running a fleet with about 15 Cummins for about 60 years I only once spun a bearing on a Cummins. And that was when a turbo blew and the driver let it run until it ran out of oil. Cummins let the 855 cu in go out of the factory with 525 hp and 1850 ft lbs of torque. And lots of guys turned them up to more than that without problems. 60 to 70 years ago oil pressure was considered an indicator of engine condition. And it actually had some validity because of the lubricants we had in those days were so bad that bearings, cam bushings as well as cranks and cam journals wore in a hurry. But with today's lubricants wear is almost negligible. We tore down some Cummis with over a million miles and bearings still miked well within spec. The few miles antiques are driven, they should last forever. The most failures I have seen is where rebuilders didn't allow enough clearance, the old iron expanded when it got hot and seized and ended in catastrophic failure. I don't worry about oil pressure but I make sure everything gets enough oil.