Thanks, you guys were right. I had convinced myself that the check valve already in my thermostat eliminated an air pocket as a possibility.
The radiator was full, but the overflow tank was empty, so I made sure my overflow tank was about 1/3 full. Then I burped the engine by unscrewing the water temperature sensor attached to the intake manifold near the thermostat housing. (Clois had suggested this technique some time ago, but again, I thought my check valve had eliminated an air pocket as a possibility). I got the coolant up to temperature, parked the car on an incline for 20 minutes with the engine off to let it cool. Then I started it back up and drove it for about 20 minutes. Once the
oil temp was up, the coolant temp was rock solid at 82-84C. I'll drive it again in the next day or so to confim the results, but so far so good.
Thanks again to all!