Howdy and welcome to Airforums.com, unit 13!
You have come to THE place on the 'net for Airstream / Argosy information.
I have seen it posted many times that in some State parks anything over 25' may be a problem. I have personally never stayed in one of those, but have overnighted in lots of commercial ones, and have never seen one of those that couldn't accommodate a 31-footer (ours).
Of course, I am sure that there may well be exceptions to what I just said, so stay tuned; lots of folks on here travel and camp!
ps: you have plenty of TV (Tow Vehicle) for that trailer. Just don't overload the truck's box by say, trying to carry a load full of rocks or several full-dresser Harleys in it.