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.