I wonder if you ordered the wrong part number. Some of these catalogs are layed out such that it is confusing as to which part # goes with which description.
Concours has the '55 hardtop rear window gasket for $72.50, part # B5A7042084-D.
In 1955, the rear window glass was exactly the same on the 2dr hardtop, 2 and 4dr sedans. The only one that was different was the glass for the Crown Vic.
In 1956, Fomoco used the Crown Vic body for the Victoria 2-dr hardtop and Customline 2-dr hardtop, so the glass for the Crown vic was the same for the Victoria. Also, in '56, the glass for the 2 & 4-dr sedans was the same as the 4-dr hardtop.
ECklers (Mac's antique auto parts) also sells it (same part # mentioned above) for $78 and some change.
I don't know how well they fit.