Hello from Colorado: You have a neat vintage Airstream. It is the last year of the leaf spring axles. Airstream went to the now Dexter "Dura Torque" axles in 1961
. I replaced the axles and shocks on my 66 Trade Wind. They were a Monroe shock, but might not work on a leaf spring axle. The shocks came with the axles from Colin Hyde in New York. He has the shocks you need. Here is a photo of my new, vertical shocks.
California's Inland RV is a big vintage Airstream parts retailer. Calling them should get you a shock part number. They are also famous for helping folks with Dexter axles.
HighSky is also a big vintage Airstream parts retailer. Maybe they can help.
Converting your trailer to Dexter Flex Torque axles is well worth it.
WBCCI #8607 VAC Region 11
KnowledgeBase trailer renovation threads: 69 Globetrotter, 76 Sovereign, 75 Overlander, 66 Trade Wind Such fun !