Since you've got plenty of room to work with, use a clutch fan that only locks up and pulls air when the air coming from the radiator is hot enough to need the extra air volume. Then build a shroud to fit that fan, if you still think you need one. The rest of the time, the clutch fan is just along for the ride, and doesn't rob horsepower or make a lot of noise. There's no point in putting up with all the noise and electrical load of any kind of electric fan that moves enough air to make installing it worth the effort, and a straight mechanical fan is "on" all the time, whether it's needed or not. My father's B-17 didn't have four 1200 HP Wright Cyclone electric motors!
Jerry
