I would like to add one more point...If flex fans were better, you can bet that the auto manufactures would have used them....lord knows it would have to be cheaper than the fan and fan clutch combo. In reality, the stock setup offers the best cooling. The only improvement you could make would be to replace it with a dual electric fan setup. However, you need to make sure it has a fan shroud that covers the radiator completly.
John......southern CA
84CJ7, 3"lift, 32"BFG, 4.10's, ARB Locker, Solid Axle's, Durabak