I don't know what the CFM is for the factory fan but it's gotta be lots.
I did put an electric fan on my '95 using a combination of junkyard parts and a Hayden automatic fan controller. (I did this years ago and can't remember the exact part number)
The fan assembly I have came from a junked '92 Buick Century with a 3.3. It works very well and is quiet but in the summer time the A/C will shut off on high head pressure as the fan just isn't big enough (CFM wise) to keep up with the A/C demands. Otherwise it's just about right for engine cooling.
I even have mine setup in the stock fan shroud mounts and two bolts in the top of the core so it's a 5 minute job to yank and reinstall the clutch fan for the summertime.
The downside to my setup is, the relay is the weakest point. it uses the generic 30amp relay that a lot of lights use, and the location I put it seems to get attacked by water (on the drivers side core support about 10" from the top. So if you go that route, either carry extra relays (I found out the hard way onetime doing some light wheeling) or cover it up somehow.
Mine comes on when the radiator temperature hits about 150 and shuts off at about 120. comes on steady with the A/C compressor and has provisions for a 2nd fan. I might look into a different fan setup to improve A/C performance when it's 110 out.
All said and done, with a cold air intake and the electric fan I can climb some hills now in 4th gear rather than kicking down to 3rd. I've picked up (seat of the pants) about a second in 0-60 times. and it's gained on average about 3-4 mpg in town and about the same on the highway. I went from 12 in town to about 16-17 and on the road it's gone from 20 to about 24.
