360 Tune Up
I took it for a drive today and drove it in lower gears and same speed. This has the effect of increasing rpm and water pump speed. Result - nada. Same temps as before. So, the pulley thing is not my problem, apparently.
I spoke to George at Champion Radiators later. His suggestion is that my shroud is restricting flow at speed. He wants me to remove the shroud and do some testing. On a 41 Plymouth, this is much easier said than done. After I get finished dreading it, I will do it and let you know what I find. Thanks for all your help.