Gale,
Indeed, 2 doors with convertible (x-style) frames were used from 1957-1959.
In 1960, a 4-door was used as the base for these cars. If you'd like to read
more about these incredible automobiles, I scanned an interesting article
about the Ghia's at the link below. Especially interesting are photos of the
"stretching" process of the '57 models.
http://www.imperialclub.com/temp/1957/1957Ghia/index.htm
--MarkE