just did this for my 73. there is a pdf file on airstream's web site with a diagram for the plug. Go to www.airstream.com,
and check the "faq" page.
What I found when I disassembled mine was that it did not match the diagram....so somebody probably changed something at some point. either that, or the diagram is wrong. Anyway, I'd double check with a meter to 'really' see what goes where on the trailer. interesting thing was that the colors on the wires corresponded to what the diagram said they should be; they just weren't "where" the diagram said they should be.