The "Alternative Fuel" listing was probably auto-generated from the VIN, because both the 4.6L and 5.4L that year are E85 capable. I don't see any indications this is a propane or CNG conversion.
Price-wise, this would be a little on the high-side without the Alluminess goodies. Book value of the base van is about $6-7k. The Quigley package was probably 12k new. I don't know how much to depreciate that part of the van, but it certainly should not be full value. I'd guess $8k is probably a fair value on a 10 year old Quigley package?
There is some good value in the Aluminess stuff, especially if somebody needs a 4x4 and was planning on installing Aluminess anyways. To me, it looks a little higher than the normal Quigley setup. Maybe the previous owner already did a RIP package?
2000 E450 dually V10 wagon