I've been on this forum for five years and I've never yet been able to convince the majority that towing an Airstream is so much more than just numbers and weight, and that a pickup truck, actually quite a dinosaur in automotive terms, is not necessarily the default tow vehicle.
I was inducted into the Andy Thompson Hall of Believe-or-Not Towing Fame at the outset and haven't looked back. With a series of videos, written pieces and actual examples, he demonstrated just what a wide open subject the safe towing of travel trailers is, and it most definitely is not tied down to what a vehicle manufacturer claims is the "Tow Rating".
My tow vehicle is a 2011 Toyota Sienna with a manufacturer's tow rating of 3500lbs. My Airstream is a 2011 28' International Serenity weighing it at around 7000lbs when loaded. The Sienna's hitch receiver has been strengthened and I use both weight distribution and friction sway control. It's also been my daily drive for the past five years.
I've weighed the setup only once, when it was new, and the axle ratings on the Sienna, front or rear, were well within spec, as was the payload, even though I calculated the payload myself as the door sticker doesn't mention it.
The setup is not illegal in any Province or State, despite what many people tell me. Browse the laws that apply to privately owned recreational vehicles and I challenge you to find any law that prohibits such a combination.
I do travel quite lightly, no generators, firewood, kayaks or bikes. My normal load is three adults and one teen, plus a Greyhound and assorted bits of camping gear.
I don't travel huge distances when towing, and it's mostly in the relatively flat and cool zones of Ontario. I have towed down to Orlando, through the mountains in Tennessee, and also to Boston, through the mountains again in Mass., and New Hampshire.
My point to this post is to say that while the OP has done an excellent job in his OP, a much broader view needs to be taken when assessing what is and what is not a good, or safe, tow vehicle.
I don't want to suggest that you should all rush out and get a minivan with which to tow your Airstream, but you should look at what else you want that vehicle to do when it's not towing and how you plan to camp (see travel lightly above) in making your choice. The stability of the vehicle and the type of hitch receiver, weight distribution and sway control/elimination
also needs to be factored in. Weight? Well yes, but it's down the list a bit.
We're into our sixth season with the Sienna/Airstream setup and have had trouble free towing all that time. There will always be those who say "You can't tow that with that" (which I hear on almost every trip). To that I would say "Where's your evidence? - My evidence is sitting right in front of you."
Happy travels, one and all. I can publish my travel schedule if you wish, you know, so that you can avoid me on the road