I have an 07' WR450 with the crappy stock tires and I am looking to change them. I ride mostly hard pack, AZ desert. What tire is the hot setup, the desert IT with the IS up front or the 739 with the 756F RR or any combination of those? What size rear are you running, 110 or 120? The 120 seems VERY wide. Thanks in advance for any and all input.