Thanks to everyone for your help. And the culprit was... the thermostat! It was in the right way, but it failed the pan-of-boiling-water-on-top-of-the-stove test. Didn't open up even the slightest bit.

Without the thermostat, the engine runs well within the normal temp range.

I guess the moral is don't overlook the obvious. It should have occurred to me to suspect the thermostat, but I discounted that idea because the part was new. New parts aren't necessarily good parts, are they? ;>)

Thanks again!

Dave LaChance