Greetings Jesse (and Mike!) !
Welcome to the Forums and the world of Vintage Airstreams!
I agree that the Airstream is likely 1958
or a bit earlier, but based on the number and sizes of the windows, I suspect that it is either an Ambassador or an Overlander with the optional tandem axles. During that time period, Sovereigns typically had side-by-side windows ahead of the door. I will be curious to learn what the VIN identifies as this Airstream's model.
Good luck with your project!
P.S.: The curbside window arrangement to the rear of the entry door makes me think that this may be a custom rather than a typical Overlander, Ambassador, or Sovereign