The tug appears to be a first-generation
Nissan Xterra. The current Xterra is substantially bigger and more capable, and has a tow rating under ideal conditions of 5000 lb.
I don't know about a 1973 (as in the ad), but current 27' Airstreams listed on their website weigh from 5400 lb to 6500 lb, dry and empty.
Time to turn on the brain and read the vehicle ratings? I do not advocate excessively large tow vehicles, and run mine to its rated limits, but this is just stupid.