[Elwenil]

The Mopar Performance fan is basically just a stock clutch fan for an '80s truck.

 

[Elwenil]

So the Mopar performance viscous fan is basically what came stock on my 1988 Dodge Ramcharger correct?

Yup, your truck would have had the exact same asymmetric 5 blade fan.

 

[Elwenil]

All of the common Mopar, stock and aftermarket, clutch fans are a viscous drive.  It's just the method used to engage the clutch automatically with the increasing temperature of the engine.

I personally do not like flex fans on a truck.  They are a racing modification that was made popular in drag racing in the '70s and '80s and basically once they spin to a certain RPM, the blades flatten out and no longer move air.  The idea being that once you are running down the strip at speed, it would lessen the load on the engine since the car was already pushing air through the radiator on it's own.  This doesn't work out well in low gears off road or while towing where high RPMs do not necessarily equate to high speeds and lots of air flow.

 

[Elwenil]

Yeah, I have a dual 12" fan setup off my old '74 W100 trail rig.  It kept the 383 cool, but it was loud as hell and you couldn't hear anything but the fans when standing in front of the truck with it running.  I've thought about using them on something else, but I just can't bring myself to listen to all that again.