Why? The stock fan/clutch and shroud will move a LOT more air through the full face of the core than any electric fan.
While you know I love ya John .....and I have gleaned a myriad of information from you in the past...... and you know I respect your input big time, but this is just simply not true anymore about mechanical fans per se. If you are talking about the tiny/cheap aftermarket fans.. then right on! But, there are great alternatives out there that make the mechanical fans look pretty lame.
For example, the Mark VIII fan will move in excess of 4000cfms and there is no mechanical fan that will come close to that output! How do I know this?.. I know the OE ratings of the BB seven bladed fan and moreover have even tested these stock fans on my own.
FWIW, Electric fans are fast becoming the defacto standard in the OE industry regardless of application. This is because the electric fan will out perform the mechanical ones at idle and slow cruising speeds, are far more controllable than the mechanical ones.. and can be used in tighter footprints.
I do agree however that if one has a pretty stock application here that the original mechanical fan and shroud system should suffice.. well sort of? As you know.... the problem with most applications here.. .everyone is adding horsepower, air conditioning and moreover the need and want to cruise in all kinds of traffic laden situations with the air a blow'in and keep those enigne temps in check! Design specs in "yesteryears applications" just was marginal at best, so cooling could be an issue with the change in the basics here. The big upgrade of course is the issuance of big aluminum radiators and this will indeed take the pressure off the air moving system to a certain extent because of the enhanced efficiency of the radiator.
Even Ford and Mercedes (these are the manufactures that I have personal contact and knowledge of) have moved their "tarmac/street" or ambient design temperature specification over 20 degrees (up) over the last 20 years! This is a behemouth target for the cooling and air conditioning system to adequately perform under! This performance standard(s) require large output (and controllable) primary and/or secondary electric fans to meet the specfication and all of this is due to more crowded traffic situations that produce higher tarmac temps.. which means the need for higher efficiency cooling systems... and not to mention lower "vent" temps inside... which translates to more heat being removed at the coil....which also travels thur the radiator system as well. It's a double whammy in that department!
And moreover....and lastly......offering empirical proof of my point(s) here..... the very Dodge Charger RT (ladened with abundant horsepower and great air conditioning) that sits in my driveway has only one fan system.. and it's electric! The output... a whopping 6600 CFMs!
Just my two sense there JohnZ, but I would love to hear your point here as always!