The DT466 is nice, and pre electronics, an extra bonus. What transmission? That will make or break it so to speak. There is a tag on the passenger side of the trans that will tell what model it is. AT 545 not so good, MT643 is a better choice. Not sure what others it could be the 2000, and 3000 series where not available yet I believe.
My bus is about the same size (11 window, 34ft)and I have no trouble at state parks.