Robbie, What year is the trailer? The hitch weight changed around 2003. The older 28' SO's have a heavier hitch weight. The newer ones are rated 1040 lbs, although when I weighed mine it was actually 980 lbs fully loaded. A class IV hitch is rated to 1200 lbs so it is no problem for the newer 28' slides.
Some of the members have gone to a class V hitch, but those are generally ones that have 34' SO's Those are generally rated about 1250 lb hitch weight. If you call Airstream they can give you the hitch weight for the trailer you are thinking about.
As far as towing with the F250, that is no problem. I tow mine with an F250 diesel and it is a great match. Just make sure you have weight distribution bars and anti sway. I use a Hensley hitch and I love it.
I really like my slide out. It gives me a little extra room in the living area. have had no problems after 3 years and only a minor leak when the slide was open during an extremely heavy wind driven rain.
Steve-- "Mongo only pawn in game of life"