The rotational resistance of an alternator's magnetic field is still going to be less than the mechanical resistance of a belt-driven, viscuous clutch and fan assembly. While I wouldn't do this on a truck with the smallest available factory alternator, my 136-amp unit should do just fine.

 

True, and not saying electric fan would be a 1 for 1 swap in h.p, but can see how depending on alternator condition/size, you would get less h.p. gain then advertised.

I'm guessing the people how notice the most 'bump' from the electric fan are those with vehicles short on H.P. in the first place, and every bit helps. Wish you were local because I'd like to measure a V-10 and do similar calcs on it as well.

I'll make a point to measure my factory airflows this weekend. Might start a thread to track the progress of this. Might be totally wrong, and if so I'll have no problems admitting it, but I don't see a huge difference between the auto fan/ hvac fan industry.

 

Ok my .02, and I know Im bringing this back from the dead but....
$500 is ridiculous for a dual fan setup. You can go to the junkyard and pull and electric fan for dirt, about $25 a fan. The Ford **gasp** taurus fan pulls 2800 CFM. Ya ya I know thats just a number and in the best possible conditions. But I have a 92 bronco and I put two fans on that one. I have not had any problems except for one blown fuse that did cause a problem. It is all fixed now

Two Junkyard Taurus fans (2 speeds): $49.95
1 Hayden dual fan control with radiator probe: $35.99
1 PAC 150A peak, 80A continuous duty solenoid (for the high speed side of the fans): 24.99 (shipping included)
1 Temp gauge, and a fan on light, : ~$30

So total was about $145 with the gauge and all, and I recommend the gauge for sure so u can keep a more accurate temp watch, and I put a little not so bright LED near the gauge so I could see when the fans turned on and off.

I put an on off on switch on the dash so I was able to switch between the high and low sides. The low side was run from the fan controller and the high side was run from the solenoid I bought and I was able to manually switch to the high side when doing some good crawling at low speeds.

Works like a charm, and I did notice a slight power difference and a decent mileage increase. All great stuff!!!!

 

Way to resurrect.
Miami, I dunno if I had said this before or not, but the 3rd gen guys are real fond of pulling out the E-fans out of a Ford Tarus. Apparently it bolts right into their setups. I dunno on yours or not.