Although Airstream never built a 'slide-in' style truck camper, they did build 2 or 3 (depends on who you talk to) truck campers on the truck frame. Sort of a forerunner of what we now consider a Class C motor home.
One of these appears in a 1958-1959ish photo of caravanners preparing to begin their caravan.
One was owned by a man who's name was VerSteeg. He was an Airstream repair/maintainence man on a couple of Wally's caravans, including "Around the World."
In later years, this unit was transfered to a later model Ford chassis and had a rear 'porch' added to the rear of it. This is the one that was in the parade at an International rally during the 1970's.
Anyway, that's the story I got when I did some research on the subject a few years ago.
Mr. & Mrs. VerSteeg are deceased so I could not get first-hand verification.
Oh yes, supposedly one of these truck campers caught on fire while on caravan, in India.