I don't know if your furnace has a heater fan or not... we have a 1963
and our little heater does not have a fan, but our trailer is so small we simply don't need a fan ~ it heats up the interior in a flash!
You might check Vintage Airstream... scroll down to restoration resources. Vintage Airstream Home
I tried to do a quick search, but didn't have enough information about what your furnace looks like to get information. If that doesn't work and others don't respond to your post here, you might check the members list and see who also has a Airstream of your style and vintage. Send them a PM and see what they have done!
Mrs. NorCal Bambi traveling in S Tardis ~ from the Great State of Jefferson