Not to be a prick, but I though I'd throw this in since it is the topic of a couple of off-road mags this month. They found that NOTHING made a difference except changing from coolant/antifreeze to straight water (no, they did not recommend doing this due to the obvious problems associated with straight water)!!!!!
They changed from mechanical to electric, tried different types of mechanical fans different types of coolants.
They did NOT try adding an accessory engine oil cooler (which I think would have helped greatly)
See Petersen's 4Wheel October 2001 (it has "ULTIMATE ADVENTURE" on the cover).