Joe -
Why don't you let the fan shroud cover the entire back of the radiator so it can pull air through the whole radiator? A 17" fan is about as large as you can go and 1" from the radiator core is about twice as far back as the stock fan set up would be on your truck. I have actually considering the same sort of set up myself for my 37. The other thing that I have considered is getting an electric fan about 17" in diameter set up in the center (top to bottom) of the radiator with a nice fiberglass shroud.
Joe
