Hi - so a quick answer is really almost anything including 1/2 ton pickups and even some minivans. See links and suggestions below.
There are LOTS of discussions here on this topic and if you ask 10 people, you'll get 30 opinions! Maybe the links below will help.
Last - if you haven't moved it for 4 years, new tires are a must and having a look at the axle couldn't hurt. You need a good weight distributing hitch with sway control (again, lots of choices and opinions - I can get like a religious war so take your time to sort through it all).
Hope this helps:
http://www.airstream.com/files/libra...c5c1005fbf.pdf
According to this chart, dry weight of your trailer is just about 5000 lbs, tongue roughly 10% of that. Depending on what you carry with it (really would have to weigh it loaded for camping) but maybe 7000# and a tongue weight probably around 1000#.
You could then use this link:
http://www.onlinetowingguide.com/gui...apacities.html
...to get an idea of vehicles that could tow that much weight.
Or this one:
http://www.onlinetowingguide.com/