i actually got an oem thermostat, that failed after 3 months.......
i then later found a writeup on the oem dual stage thermostat, i have since been running that and havent had any heating issues since (been in about 2 years now)
the dual stage thermostat has a bypass, to prevent possible overheats
part number of the upgraded dual stage oem is 90916-03070
http://www.4crawler.com/4x4/CheapTricks/index.shtml#Thermostat