The Wan's like the Pirelli Scorpion Rally Pro for the front, I tried one on the front of my 1150 with a 21 and really like it too. Hooks really good in sand too.
I've run the 908 on a lighter bike and hated it, no traction. I've heard that it's okay on the heavy bikes.
Your first set ought to be shot by Moab, look for a Dunlop MX71 for the front and a Maxxis Desert IT for the back(don't worry that a 120/100 is the biggest size, it's a massive tire)...awesome pair of tires for the west.