I have a 512 inch big block in my '65 Coronet. Mechanical fan, shroud and a 22 inch aluminum radiator. I have a 180 thermostat in there and it doesn't get much hotter than 180. My EFI system has a data logger so I can review how hot the coolant temp is after a drive. Hottest I've ever seen is 187 degrees. It gets the hottest if it is sitting in the sun at idle after a hard drive. If the car is moving then the temp stays down around 180. I think that having a correct shroud is super important. You also want some pump speed so make sure the pulley ratio is correct. For a street car you should be driving the water pump a little faster than the crankshaft. The lower the engine speed then the more pulley ratio you want. You need water flow thru the engine in order to remove the heat. The more water flow the better as long as the pump doesn't cavitate.