You need to check your coaches GCWR and actual weight, and also the hitch rating. Most C's are limited to 5000 lbs or less towing because of the hitch rating.
The GCWR on the E450 has been steadily increasing toward 20k 04 22k (depends on year and configuration) while the GVWR remains at 14,000 last I knew. That suggests it could tow as much as 8000 lbs if the hitch and the extensions to the frame where the hitch is mounted could handle that much. But I don't think anybody is shipping an E450 based coach with more than a 5000 lb receiver on it.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL