I think what will work is the 19.5's and that will allow me to lower the bus a couple inches so the bottom step isn't 10 inches off the ground. But with so many variables and such I think I will get the beast moved onto a hard surface and do some more measuring. I might ultimately find a P30 step van with disc brakes and just buy the whole thing and do a frame off or total frame swap. So much to think about with these big guys. Maybe I won't be getting her running to be ready for summer. Not that looking pretty was the plan this year, but I would like to at least like to drive it. I really appreciate all the input and feedback here guys. Especially Grigg. Been reading his tech pages over and over for more insight and it is most helpful.