I felt I recognized that song's origin the first time I heard it. "...watching those old raindrops fall" - raindrops were(are?) radarscreen blips. There were 73 on the Pueblo but it went out of San Diego rather than San Francisco. Someone listening to that song who did not have the NSA/ASA/AFSA/USNSA experience could well think it is allegory or describes something in the real world but would not have the background to recognize the Pueblo.
The Pueblo crew size was 83, not 73.
http://www.usspueblo.org/