Okay, so I didn't do this myself. But I did find out a DIY Post on a Jeep forum to swap out the mechanical fan for an electric fan.
The fan operates on an on-off-on switch, up if for high, middle is off, and down is low fan speed.
Not only does this benefit in quicker warm-ups, but since your mech. fan runs off belt speed, if you run low rpm's at highway speeds (i do) your Mech. fan isn't cooling off the engine efficiently if your going up hills and generating heat, but the belt speed is the same. This isn't much of a problem in the ZJ's, but for the TJ's and YJ's, their cooling system could use a bit more work.
With a full grille block in the summer, the temps can start to rise a bit, though I haven't seen temps over 200, could use a bit more cooling (oil temps are high and I'm getting low oil pressure from leakage). So if you are out wheeling or rock-crawling, and your giving your engine hell but the rpm's are in the low range, you need a cooling fan that can run on high, because your belt is making your mech. fan run slow. Well here's the DIY for an E-fan swap. It involves taking one out of a 3.8L in a Ford Taurus/sable/lincoln etc. Two bolts and you cut the wires.
http://www.jeepforum.com/forum/showt...ghlight=taurus