At startup, no oil pressure, can hear lifters clicking.
Turn it off, turn it back on, oil pressure comes up, no lifter noise.
Oil pressure is a little under 40 per the gage.
Give it a little gas and at somewhere between 1000 and 1500 RPM the oil pressure goes away, no lifter noise.
I'm going to repeat that--it HAS oil pressure at IDLE.
ABOVE IDLE it has no oil pressure.
Oil level is right at the top mark on the dipstick. I tried changing the oil and filter and that didn't help.
Haven't put a mechanical gage on it yet--the lifter noise at startup and the consistent behavior suggest that it's a real problem and not just the gage and I don't have a mechanical gage.
Problem started right after I replaced the plenum pan and gasket.
My inclination is that something or other (a lump of gasket, a leaf, a squirrel, or whatever) managed to get into the oil pan while I had the manifold off and is now partially obstructing the oil intake.
My inclination is to drop the pan and see if the strainer is obstructed, however if anybody has some less messy alternatives to try that don't involve working underneath it in the pouring rain or riding a motorcycle down to the parts store in the pouring rain I'd be ecstatic to give it a try.