with 34's, you will rub the leaf springs when you turn lock to lock, I rub with my 33's and I have a 2.5" offset. mine are also 12.5 wide, but when you reduce the tire width, and make it taller in the same distance, you are in the same sense putting it back to where it would be, cut an inch here and replace it there... make sense? height is different, and yes, you might be able to clear 34's just fine in the wheel wells after some trimming, but... do some measurements and go from there. I was not going to be able to clear the 35's with 3" backspacing on the springs, the body was missing about 3" of fender wells.