I should be able to figure this out, but I guess my weekend brain is not up to par! Here is the serial number as it appears on a '64 Safari:
041 S 3176
Here is the link to the Vintage Airstream Photo Archives 64Safari
So I believe the serial is saying a Landyacht Option made in California. Any other information from these numbers? What does the "6403" under the first set of numbers mean?