I have had verry good luck with flex-a-lite. Have a set of twin 12" fans on my sb s/c s truck. Never over heated. Also had a set on my monte carlo with decent power. Not plug in, but could fit, and be wired in easialy.
As I see it. As long as your radiator is big enough, and you have the right thermostate. The fan just needs to be big enough to move air equaling the hole surface area of the radiator. Twin 12" fans set at 165* off temp, should not have any problems.
Had a really bad overheating problem in my monte. Took the belt driven fan off, and added a flex, and never had another problem. Even with the a/c running on a 90* day. No more problems.
his may have just been a bunch of crap to some of you. Just giving my opinion.