I have also been looking at getting an MH. I prefer the 8.1 with the Allison transmission. I have been told the Allison assists in downhill speed control. This actually has proved true in my 2005 Silverado 2500HD. Anyway I prefer Chevy. My dad has the V10 in a 1999 33ft MH and has not had any problems.
Found a couple of Gulf Stream Class C based on the Kodiak with the 8.1 on rvtrader.com
You will find those that prefer Ford and those for Chevy. After 2008 or 2009 Chevy quit making the 8.1L for MH or pickup use. You can still find them if need a rebuild.