When I was flying a jump plane 182 many years ago, I remember at 500 feet reducing rpm by 100. But, throttle stayed wide open till altitude was reached usually 7500 feet.
It's there, then, on front of engine, pilots side, below propeller hub.
https://www.rapcoinc.com/images/vacuum%20pumps/RAP215CC-9.gif
Have you seen this?
https://150cessna.tripod.com/oilflow.html
Do you still have a vacuum pump? If you do never mind, but if it's been removed I believe a plate has to be installed or you will have a loss of pressure.
You asked me earlier, but I had to ask my son, because I haven't flown it in a year or two. He said the oil pressure would run about halfway between the bottom of the green and the white line. That was at cruise power in Florida.
It would be a half a needle below the min line after a couple...
The B-29 was researched, designed, and built by professionals. As was the Wright 3350. That didn't preclude many crashes and deaths before they entered service for defects.
Was the previous owner running the phillips oil. I have heard but no first hand knowledge that changing oil types might be a no no. Ours does run right on the red line at idle when hot. If you live in a colder climate the 20x50 might be better because it will flow better at colder temps. At 200...
What oil are you running?
If it's still a mechanical oil pressure gauge, it's possible for air to get in that line and then you'll read lower than actual pressure.
Have the cylinders been off. At 700 hours there is a good chance you may have a piston pin stuck. That will cause non magnetic...
Ultimately the captain makes the final decision, but. The company maintenance, and flight operations, dispatchers, and the other crew members on board have a great deal of influence on the decision.