But we are talking about an old A-Body, the radiator is wide open. No way is the air going to miss the radiator or go around it at 65 mph without significant modification to the grille area or the radiator being physically blocked (packed full of mud and bugs, covered with a plastic bag, cardboard or other large road debris).
The fan is also on the backside of the airflow so the radiator won't care what speed it's spinning when the car is traveling 65.
