I agree with the other replies.
The V10 2-valve is the only Triton engine available in a van & cut-away van chassis because the 3-valve version is too large to fit inside the engine compartment. The V10 in an E350/E450 is very reliable and also powerful. The only complaint people have with the V10 is that it is very loud when accelerating or climbing, and the passenger floor gets quite warm from the exhaust system passing underneath it. But it is a great engine.
If you can get a 2008 chassis or newer, easily identified by the current-day dump truck style front grille, you'll have a more capable chassis with regard to the weight it can handle. And I think we would all agree that "weight" is the number-one problem with class C motor homes. By the time you add people, water, food and gear, most are over-loaded.