Electric Fan and High Amp Alternator

[beaterC10]

I have seen a thread here about using a Jeep fan and a few on the net about using a Lincoln or Taurus fan.

Most claim you can pick up a few mpg with an electric fan. Is that really the case? The reason I question this claim is that you are trading power loss from spinning a mechanical fan for the load from spinning the alternator. It seems any savings would have to be the result in an efficiency gain with the electric fan.

The next question is about finding a big amp alternator to run the fan. What little research I have done suggests a CS144 alternator would work. It resembles the alternators used on our trucks with a bigger case. Were these used on any of the 73-87 trucks? Any other suggestions for a non-chrome 3 wire big amp alternator?

I am old (middle aged) and my truck is a daily beater so chrome and 1 wire alternatives are of no interest to me.