I am a DuraMax/Allison guy but GM isn't building the Kodiak Chassis any longer so I bought an 08 Ford F550 chassis/coach. I am nervous about the 6.4L and would not own a 6.0L because they have a long history of problems. You only have a couple choices, Ford, Navistar and Freightliner are the only ones I can think of right now. All of the above will be in the Super C catagory. The M2 Freightliner would be my chassis of choice if I had to make the decision today.
Host is currently not building any motorized units, then you have the Thor 33' Super C but Thor is getting a lot of bad press right now and then there is DynaMax. They build a nice smaller M2 class C and also they have the F Series Isata on the Ford F550 chassis with the 6.7L. Sounds like Ford finally got the diesel right with the 6.7L and I hear the new generation 6.7 is better than the first.
There is also Nexus with the Navistar chassis. That unit looks good as well but if you want to stay a bit more compact then DynaMax is the way to go.