any thoughts, my bbc get hot @ idle

have a 39 chevy coupe with a 1970 454 bbc, high floe short water pump, walker corba z radiator, a 16" 3,000 cfm electric fan(puller). when driving the car is runs 190 degrees or less, it starts slowly gettting hot when i am in alot stop & go traffic or @ car shows following crowds, as soon as i can get up to 45mph or higher the temp drops down to normal within 5 min. I am guessing the problem is not enought air flow at slow speed, any ideas that will work to keep the engine cool a idle? thanks