Plain 69 is right about most of your aftermarket electric fans in a hotter climate - they just don't cut the mustard by themselves and often have to have another fan to help keep things cool.
HOWEVER, I can recommend one single electric fan that has worked exceptionally well on my 10-1, 38 degree'd, 400+ horse 383 stroker. I live in Houston, Texas where the mercury soars for months on end it seems. You need to check out the Black Magic fan from Flexalite. Jeg's and Summit carries it and I think it runs in the $180 range. As long as the rest of your cooling system is up to the task (ie. strong water pump, big radiator) this fan pulls some serious air thru the radiator and it works well. I think it moves something like 2,800 cfm and sounds like a big flex fan when it runs. My temps NEVER get over 180 degrees while cruising day or night during the summer here in Houston. FYI, I use a big Griffin 2 row radiator and an Edelbrock water pump combined with a 160 thermostat. My fan is positioned at the top right corner of the radiator (the hottest spot). I bump up to a 180 thermostat during the cooler months, like now. Otherwise it runs too cold and never gets above 160. Hope this helps.
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1970 Malibu - 383 'Fog Fed' Brute Force Chevelle. Houston, Texas...Gold Member #39