Where to advertise my vintage 1963 Airstream ?

^What BB said. Put it on FB and Craigslist.
Idk why folks actually pay a bunch of money to sell stuff private party.
Maybe some boomers don’t use those platforms, but the majority of adults do, in my experience.
You could have had it listed for free or $5 in the amount of time it took to ask the question here.
Unless maybe you’re marketing it as a museum piece or something…but bottom line, it’s a camper and the $ spends the same whether you think it’s special or not.