Finally found the cause of my overheating

Two weeks ago I was headed home in my 1964 Dodge Dart Convertible from the local dart game night at the brewery near my office. To my surprise I see the temperature gauge flirting with the end of the "OK" temperature range. I nurse the car home with the heater on making sure I don't exceed the high temperature level.
Last weekend I check the thermostat in boiling water, flush the system, add fresh coolant, and viola everything looks great. Drive to work yesterday morning and all is good in the world.
Last night, I am again heading home from darts, and guess what, over heating again! I pull into a gas station to fill up, and let the engine cool down. As I pull out something occurs to me, turn the headlights off. Sure enough, head lights off, engine cools down. Turn them on, and needle starts to climb.
So do I need a heat shield for my headlights!? :lol: