I've had or have pretty much every Engine in this discussion so I'll toss in my unadjusted $0.02. If I were buying a van with any chance I might be converting it to 4x4, and any chance I might be doing some towing, I'd steer away from the 5.4. I never really realized any significant fuel savings especially if was expected to pull any load. And to be honest, a loaded up passenger/camper van is pretty much a load in itself.
The 6.0: Diesels are cool. Modern diesels are powerful and just about as responsive as a gasser now. Modern diesels will also drain your bank account in nothing flat when something goes wrong, because when it does go wrong it tends to go wrong in a big big way. Unless you are pulling a lot and pulling heavy, it's pretty hard to justify the initial and potential expense of the modern diesel.
7.3 diesel: Durable and when something goes wrong it's usually not as wallet killing as a 6.0. Btw, did the 6.4 ever actually come in the E-series? If it did, see issues related to 6.0 r.e. cost to repair and necessity in the platform. The 7.3 can't make the power of the other two, as easily or cheaply, but it doesn't really need to. It's plenty capable, especially if you aren't planning on towing heavy all the time. Biggest con is you want a newer van, and the 7.3 was shelved a decade ago.
V10: IMO, this is where you're at. It has the grunt, the fuel mileage was not significantly different between it and the 5.4 when just cruising about, it's durable and long lasting, not crazy expensive to fix the things that tend to go wrong, and it can be had in a late model van. What's not to like?
Short version is I would not opt for a late model diesel if I were not intending to tow a lot and tow heavy. If you aren't it's wasted money and financially risky for no real benefit. To me the 5.4 is saddling you with a lack of available power for not enough fuel savings to warrant it. The 7.3 comes wrapped in a skin too old for your wants. The V10 has more advantages than drawbacks and would win the day in my book.
My DD is a F-450 with a 6.4 that will pull down a mountain. The high pressure fuel pump failed when it was idling in my driveway. If I trusted Ford enough to take it to them for repair that is a $12,000+ job. I don't so I took it to my trusted diesel shop and paid a bit more than half of that. I have an F-350 with a 6.0 in it and the high pressure oil pump failed in it while twoing a trailer through PA road construction, which backed up traffic for miles since it was one lane, no where to go, and getting it a tow comapny that could handle the combo took some work. Ford took a stab at that one, charged me $4,000 for the honor, and failed to find/fix all the bits the initial failure compromised, which led to another failure shortly thereafter.
You see where I'm headed? My trucks pull, they pull a lot, and then tend to pull heavy. Where a diesel shines. If you don't need it, don't risk it.
my email should be in your inbox by now I just resend it.
