I find it weird you are noticing that big of a difference... not a huge tire size change, especially for a 6.0. I went from 31.5s to 35s with my little 5.4 with 3.73s and i felt the difference, but its not much worse driving (just mpg). If you want to regear you could... but its about a grand an axle, so double it if you have 4x4.