The 460 will depend on if carbed or fuel injected, I would recommend you go to a ford based website such as ford truck enthusists and ask your question there. If you find something you like but it has a carb, there are FI kits available if you say your other 1/2 is capable of mech work. The v10s late model are OK but I would still rather have a diesel. we have 2012 e450 with the 3 valve V10 cant really say anything about the 2 valve jobs.
The chebbies referred to are later models than you are looking for I believe? There are some diesel rigs out there but they command a high price and really are not all that powerful in a van/rv. Most likely you would find an old 6.9 or early 7.3. The 7.3 can get some aftermarket help, not much the 6.9.i