From everything I've read, and diesel-heads I've talked to, an sct tuner is the way to go with the 6.0. Nobody makes anything specific to the van and having a custom tune written from your OEM tune is the way to go.
Mine was written by Eric and Innovative Diesel. The van programs are exactly the same as the truck programming, with slightly less aggressive fueling tables. From the three or 4 outfits that write tunes for the SCT, they all indicated that the higher power programs will always yield the best mileage, if driven with a light foot. My economy is about 60rwhp over stock, so it works well for daily driving and towing. The EGR is turned off in the tune in case I want to delete it later. I also have an Atlas40 FICM tune and that provides quicker turbo spool up and throttle response. But hey, I just blew an injector on #6 at 90,000 miles. Was it the tuning or just fate? Don't know but I'm not changing anything except dishing out the coin for a new injector, new standpipe and dummy plugs, and a blue spring upgrade.
In case you still need some additional reading after the links E350 provided here's a poll on the different programming options and plenty of follow-up. http://www.powerstroke.org/forum/6-0l-p ... ammer.html