Engine should run @ lower revs, a larger tire makes fewer revs per mile.
I'm running 33's on mine(stock gearing) & just put on 3000+ miles to Moab & back with no issues other than about 11% speedo error(reads less than reality) & poor mileage.(trip avg. 14-15)

Larry W - 99 VX s/c
3" lift w/trimming & BFH mods, rollin' on 33/12.50x20" Nitto Mud Graps. Indy 4x h-d tie rods, lower links & a bunch of other stuff that put the hurt on the wallet.