Re: Suggestions on Gas or Diesel van w/built in generator
The 5.4L tends to get about 1-2 MPGs better than the V10, but a lot depends on the final configuration. A heavy, lifted 4x4 probably won't do any better than the V10. Both will be guzzlers.
But when I've rented newer V8 vans for larger trips, they average 18+ MPG, fully loaded. Granted, its mostly highway driving, but we're talking southern Oregon highways which aren't really flat. I would expect 16 MPG from a newer stock V10 van being used on the same conditions. My V10 maxed out at 15.5 MPG when it was stock (or 13 MPG tops now), however the newer drive-by-wire motors do get a little better because they completely de-fuel when coasting, and maintain closed-loop operation even at WOT.
I also took my dad's 5.4L van with my Weekend Warrior once (snapped off a pinion gear tooth on my van) and it burned quite a bit more fuel towing that heavy (~11,000 lbs) compared to my van.
The 5.4L is not as easy to convert to 4x4 because it does not come with the TorqueShift. The 4-speed required transmission disassembly to replace the tail-shaft. The TorqueShift does not. Also Tow/haul mode with grade braking on the V10 is pretty nice.
2000 E450 dually V10 wagon