I do not know the answer to your question.... but have you checked Vintage Airstream pages for schematics of your frame? I am not sure they are there, but maybe??? VintageAirstream - Restoration Resources
Do you have an owners manual for your year? If all else fails you will need to be double sure you are finding your frame... might have to peek under the belly pan to find the right spots!
I did a search and found these items:
From the Airstream Store ~ repros of owners manuals:
Airstream :: Store
Q: I need an owners and service manual for my Airstream. Where can I get one?
The first owners manuals were published in 1964
. Prior to that, the owner received a brown envelope containing parts lists and other helpful information on the accessories in his trailer. The VAC has started making these available in the Members Archive section. A service manual with instructions for performing service operations did not exist until 1972.
You can get photocopies of owners manual (1964+) and service manuals (1972-1986) from:
Helen Davis Secretarial Services
PO Box 484 Sidney, OH 45365
Prices are about $33 and $70 respectively. After 1986 the Owners Manuals included available service information.
Hopefully someone will chirp in with the exact answer! You might do a search on a frame off restoration of your model to see if anyone has photos of the frame.... Good luck!
Mrs. NorCal Bambi (traveling in S Tardis ~ from the Great State of Jefferson)