If they won't give CFM rating, look else where. Get the highest CFM you can and don't use a full shroud. There needs to be room for air to get through the core when out on the road. At highway speeds you could turn the fan off and likely still cool the engine just fine. With a full shroud, that won't happen! You may have room on the sides for the fan to hang over, this will allow even bigger diameter and more CFM.
