This trailer only weighs 5,000 lbs dry
And so add another 2,000 lbs if you load it to the gills.
You CAN tow it with a 250, but aren't most V-8 150/1500 class (½-ton) pickups rated for over 7,000 lbs?
Now if you were talking a NEW 31-footer, it would be a different story. Airstream trailers bulked up over the years, and if you were looking at say a 2003 Classic 31' model, the dry weight is 7,200 lbs, and gross weight is 8,700 lbs.
But think back to 1974: what do you think they towed it with then..?
If it's to be, it's up to me.