I checked the following site: http://www.vintageairstream.com/archives/index.html
which is the vintageairstream.com site.
It has 1957
as the last year "listed" for the Bubble. Bubbles were made that year in both California and in Ohio. From what others have posted, there were often differences in the trailers produced in the two production plants. They weren't necessarily the same. How long is your trailer? Bubbles were 16 feet in length. In 1957
, there were also trailers referred to only as "18 footer," then 22' trailers in Caravanner and Flying Cloud models, followed by an Overlander 26' model which was also produced in both California and in Ohio and finally a Liner 30' "Soveriegn of the Road."
shows a Pacer 18', two more 18' models referred to only as "18 footer" made in both California and Ohio, 22' in Custom, Flying Cloud, World Traveler and Caravanner, an Overlander 26' and a Liner 30'"Soveriegn of the Road."
There are photos of the 1957 Bubble and of the 1958 Pacer. There are also photos of the 1957 and 1958 trailers referred to as "18 footer."
Someone with more definitive knowledge than myself will have to help you if viewing those pictures doesn't resolve your questions. Hope this helps.