Dave a simple search of http://www.google.com/ for "ford conversion van
price" returned over 330,000 results.  Here are a few links.

http://www.olatheford.com/vanin.htm
http://www.soundford.com/conversion.htm
http://motors.listings.ebay.com/Ford_E-Series-Van_W0QQfclZ3QQsacatZ6224QQsocmdZL
istingItemList

Good Luck

Steer clear of the Dodge Van.  It is nothing more than a cheap
commercial vehicle that Dodge added a bit of gingerbread to, in order to
sell it as a passenger vehicle.  They have got to build the cheapest
piece of garbage on the market.  They have had a rust problem on the
rear gutters for over 10 years, and have refused to spend a dime
eliminating the problem.  Everything about the Dodge screams cheap.  I
have recently owned a Dodge 1500 p/u and still own a B1500 Van.  The p/u
wasn't anywhere near as bad as the van.  It would have to be selling at
below 50% of market before I would ever touch another Dodge truck or
van.  I have gone back to Fords as I have never been disappointed in
there products except once.  Well maybe twice, if you want to count the
poor paint job on a 1990 Lincoln MKVII that I bought new.  But then, a
lot of Ford vehicles had paint problems in the early 90's.

Most Ford conversion vans were/are 150's. The heavy-duty ones were/are
350's. I don't think f250s are used for the standard conversions...the 350s
use a heavier frame if I remember correctly. I haven't researched it, but I
never see f250s as anything but work vans w/o side windows.

The factory Chateau package (pretty nice, and a lot cheaper than a
conversion package) is not available on 250's, only 150/350.

I used to have an E150 Chateau which served me well, and for my next truck
might consider a E350 Chateau with the Quigley 4wd conversion (depending on
finances, that is).