That trip sounds amazing!
My friend was one of the video people on this trip:
http://www.drivearoundtheworld.com/
He did the Longitude portion. Approx 15 months! The footage was purchased by Discovery Channel and they will be broadcast about 8 episodes everywhere on TV EXCEPT here in the USA.
That is supposed to happen end of 2007. I'm sure after it is well received in Europe/Canada/Asia/S.America/Europe/Africa.... the people at Discovery will see the light. They averaged about 10mpg and with 4 trucks... you can imagine that added up fast.
On another note: I hope that you speak Spanish. My friend was able to get the team out of many "jams" because he spoke Spanish. Meaning at borders and by harassing police. Mainly Mexico had corrupt police wanting $$$. Other places he mentioned weren't bad at all compared to there. Also carry a copy of the title of the vehicle. This can be a major PITA at borders if you can't "prove" you own it.
Also if you don't have lockers in the front/rear... it is a worthwhile investment. Well worth the $$$. Carry 2 spare tires if you can. You are running 285/16 which is a common size.. however you never know where you may have problems. MTR's if you hit some brutal terrain are known for issues. People seem to prefer the Toyo MTR's. Plan on getting worse gas mileage then you are used to being loaded up and roof carrier etc.
Wish I was going! Sounds like a spectacular trip. If you are leaving in October you may want to search/PM on here with some people have have done long trips up to Alaska. I'm not sure what the surroundings will be like then... ie impassible/muddy/snowy etc.
PM "pismojim" on here. He has been to Alaska with a group and can give you some insight which can't do anything but help.