I agree that the Ford (or likely the Chevy equivalent) should do fine in general. The Ford V10 is a relatively high-strung truck engine, and it will be running at what may sound like absurdly high rpm's when under heavy load, but it's designed to operate that way.
Do take care to watch the hitch ratings, including the tongue weight (which is sometimes relatively low on class C motorhomes). Also pay attention to make sure the rear axle doesn't get overloaded due to the long overhang between it and the trailer hitch.
For launching the boat, it may be well worth considering having a front hitch installed so you can nose the trailer to the water instead of trying to back it down, especially with the long overhang in the back. Maneuvering in general around boat ramps will be somewhat of a chore, if only because the turning radius of a class C motorhome, at least one based on the Ford van chassis, is pretty abysmal.