I would confirm temp with a known good mech gauge. take stat out just for an hour for a drive to see if it is opening all the way. take the fan off & go out on the highway quickly to see if it is restricting airflow. what do the plugs show? As said is mixture/timing in the ballpark. at the highway speed where it runs hot you might duplicate that RPM in your driveway & see what the adv is at that point (if you have a dialback or timing tape). post any news. EDIT what does it run at at lower speeds? MORE EDIT is the rad fairly new? if in doubt you could run a garden hose in the top & get a ballpark figure if it is flowing reasonably enough out the bottom nipple.