It is common for the coach to be a different model year than the chassis. This happens because the chassis is built first (by Ford in this case) and then sold to Fleetwood/Southwind, who later builds a body on it and sells it to a dealer. By federal law, the final manufacturer (Southwind) assigns the model year via the manufacturer's Certificate of Origin, so if Fleetwood sells the coach as a 2007, that is what the entire vehicle is for legal purposes.
Depending on your expectations, it may well be true that you have "problems" climbing that grade in Albuquerque. Some of the Southwinds are pretty large coaches (you didn't mention a length or weight) and they all won't race up that grade like a passenger car might. I have a 2004 American Tradition with a Cummins ISL 400 and it doesn't exactly fly up it either. [By the way, my 04 coach has an 03 Cummins engine in it].
As for improving performance, the most common solution is probably the Banks Power Pack
. There may be some "super chips" that could be used to up the V10's heavy load performance as well.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL