It is possible to lift a bus.
All that you need to do is put a block between the spring pack and the axle.
I owned a Thomas RE that had blocks under the spring pack on the front end. For some odd reason the bus was ordered with a double bumper on the front end. Taking the blocks out meant I scraped the front bumper on a lot of curb cuts. But putting the bottom step four inches closer to the ground was a big improvement.