I'll throw this out there just for consideration. Many are aware I believe of OEM designs that allow high speed air to bypass the fan with shroud flaps to allow extra air flow when car often is developing its greatest's HP output. Nobody can argue that helps, but it's my contention it does not help much. So, a fan at higher car speeds actually creates significant air flow blockage thru the radiator. Now if your car at low/idle speeds has no cooling issues whatsoever. and you notice any temp rise at speed, a better solution might be this. A circular well-designed close-fitting shroud only slightly larger than the fan to allow just enough clearance from motor movement/vibration and simply allow the rest of the unshrouded radiator be left completely open for unobstructed vehicle movement air flow. The fan moves nearly the same mass of air, it just concentrates [t on a smaller area of the radiator, and if shroud is well designed/fitted, it might actually move more air. The real gain is at high speed it blocks less air. It's also the easiest shroud to fabricate whatever the material, steel, alum, FG, CF, etc.
Smokey Yunnick at Daytona back in the day was required to run a fan. The officials complained his very flat fan didn't move a lot of air, his thinking was that is why the car moves I believe.
