Thanks for everyone's replies about overheating. Yesterday a friend and I replaced the head gasket(copper) with a new composite type from Mike's, and also removed the air filter assembly. Drove it about 30 miles as fast as I dared on these 2 lane roads. No overheating ! Timing is dead on. Checked the plugs before and after the changes. Before, they were black, especially around the outside edges; after the changes, the plugs were a light brown color, which tells me that due to the air filter, it was running rich. So afr, looks like the problem is solved. By the way, this car has a new radiator, but as a precaution against grease, I cleaned it out twice with Dawn liquid.