Great White Northeast, and East Coast, doesn't tie your whereabouts down very good.
So get the yellow pages from the nearest bigger city and see if there are any Ford Truck (only) dealers. Portland, Portsmouth, Boston, Providence and Hartford - that size city. Then look up that dealer on the web and see if their website includes in-stock inventory of "commercial trucks", including F-550s. Then call that dealer and ask if there is a truck-only Ford dealer nearer to you. Anyhoo, call a nearby truck-only dealer and ask if they have any F-550s in stock with XLT trim, diesel engine, and whatever else you can't live without. If they say no, ask them to do a "dealer search" of the Ford dealers in New England to try to find you a truck to buy. Of course, if they find it, you'd be obligated to try to buy it from them.
One huge Ford truck-only dealership is Heintzelman's Ford
2424 N John Young Pkwy
Orlando, FL 32804
(407) 298-1000
http://www.truckstruckstrucks.com
That's East Coast, but not exactly the Great White Northeast. They have lesser vehicles in their on-line inventory, but I can't get it to work for F-550s. So if you can't find a similar dealer near you, then call Heintzelman's. they probably have what you want. And if they do, you need a trip to Disney World anyway.