[blizzardND]

2 things come to mind about the E450 and diesel power.

The first is front axle weight, when you stretch a chassis for a RV weight that normally would be carried by the dual rear axle is transfered to the front axle as a matter of weight time distance. because of that if you look at most Class C Rv's you will notice the have a lot of rear overhang to balance (teater- totter) sp? the front axle wt back on the dual rear. If you add the additional weight of a diesel engine, you have to add more counter weight and that starts to put a E450 axle over its limit.

2nd thought, I considered retrofitting just as you are but by the time you add up all the costs for the new engine, and everything that goers with it (I even considered buying a complete truck and doing a 2 engine swap and sell the formerly deisel pickup now with a gas engine) Then figure the difference in mileage and the number of miles one would have to drive just to break even on the install costs You almost have to drive your RV hundreds of miles daily just to rack up enough miles to make the conversion pencil out. (Then there is that pesky physics problem above you still have to work out.

good luck with your choices lets see what you come up with, but I think if your thinking diesel, you might be right in the cat birds seat to buy a class A pusher for a song in this economic environment.
-blizz