Dart cooling system

I have a 67 Dart with a 340 , 4 speed and 4.56s. I have Aluminum heads and aluminum radiator. I have been hearing so many different answers and I need one right one. What's the best coolant to use for the iron block but aluminum heads and radiator? I was told Prestone pre mix 50/50 but I figured I'd ask this group , you guys never let me down. Thank you.