I added hp, now I need to add cooling.

[hotrodhomi]

I'm almost done installing my new engine and I'm a bit worried about the amount of cooling I have. My new engine is about 410hp and I'm running what I believe to be a 4 core radiator. My previous setup ran a 18" clutchless fan with out a shroud. I was thinking about just adding a shroud, but at $70 for the shroud I was thinking about skipping the shroud and going straight to an electric fan set up with the appropriate shroud. Although I'm hoping to keep the cost at less than 3 bills.

So the question is, how many CFM's does the electric fan need to cool my blazer? Do I need a dual fan setup?