I have a 2007 350 SL Dynamax with 350hp Cat diesel and 3000 Allison Trans. We love the Dynamax we get about 10 + mpg coming home from Oregon where we bought it. The Dynamax is on a M2 heavy duty Freightliner chassis rides great very little noise. I would ask around about the gas /diesel but the gas model super C's got in my way climbing the Rockies. The gas models as far as I know don't have jake brakes so plan on pushing and praying going down steep grades. Doesn't matter which one you pick just have fun with the family and see things you never seen before. You may want to ask if anyone has had any problems with the wind push the RV around on the road. I was in Yellowstone and talked to a guy who owned a Chevy Kodiak GAS he was having problems being pushed around by tractor trailers and higher wind speeds.