high speed overheating

I just put on a smaller pump pulley and it helped e little. i just ran 70mph for 10mi in 80 degree temp and it went up to 200. timing is 35 total. hose has the spring and temp gauge is accurate. radiator went to shop for flushing and they said nothing wrong with it. spark plugs look the right color.havent changed thermostat for a wile but it dose regulate to 180 quite well at low speeds. I gota get out the infare thermometer and play with it. I need a radiator for another car so i am tempted to buy it to try in this car.