YOu can fit up to a 285/75/16 on an OBS with no lift. It will rub slightly on the fender lip but that's nothing that a hammer can't take care of. I don't know why you would want to put a body lift on and put stock size tires on it. A lot of Z-71's came from the factory with 265/75/16's. I lost maybe 1 mpg when I went up to 285's but I think that's mainly due to the extra weight of the larger tire. On the highway my truck pulls harder and stronger than it did with the 265/75's. Putting a body lift on will only decrease your gas mileage b/c it makes your trucks aerodynamic profile larger.