After reassembling the engine with the new front cover, I ran it in for 20 minutes, changed the oil, and started it back up.
This is with the water up 185. Oil probably a tad cooler since this was just running it in the garage, but 20psi warm idle? I’ll take it.
After a 20 minute drive around town to get some heat in the oil, I’m still showing 15. So that problem is solved. Now to get the break-in miles done.