@71Polara383 adjusted the carb this morning, and while that solved a slight roughness at idle it did nothing for the overheating (not that I expected it to). I then drove for five hours through Illinois and Wisconsin, on a mix of roads and terrains, with outside temps ranging from 88F in Illinois around 2PM down to 72F in the early evening in Wisconsin. I had initially planned on going to the Waupun show, but I bailed out to trouble-shoot the car instead.
Medina ran smoothly and strongly, and we had fun -- but the temp rose whenever the engine got exercised more, and dropped when I let it relax. No issue whatsoever on county roads at legal speeds, none while idling in traffic in downtown Milwaukee. The highway was a different story. Driving back on I-43 in Wisconsin, I got to the same highish temp as yesterday (75% of the way right between L and H) just keeping a steady 70 (cruise control on) when going uphill. Time for the rad to be rodded.
Here is a photo taken in front of the cow statue in Harvard, IL on the way up to Wisconsin.
View attachment 384930
Yes, your symptoms indicate restricted flow in the radiator, so rodding it out should take care of it. What are the numbers on the top of the radiator - is it a 947 (last three digits)?