1948-49 buick-cadillac X frame,convertible topframe interchange

[chas]

do the caddys and big buicks share the same body frames and convertible top racks in 48 and 49?

[J. Friedman]

I'm fairly certain '48 Buicks were different, so whatever body and top parts will interchange with '48 and '49 Cadillac convertibles would only do so from '49 Buicks. 

[Doug Houston]

The '48  Buick still used the 1942-derived "C" body, and the '48 Cadillac used the new "C" body.  There is no similarity between the two bodies.

Further, even year for year, Buick had a totally different frane from Cadillac. Buick had all-coil suspensions, while Cadillac used longitudinal leaf springs in the rear. While Oldsmobile 98 for 1948, had the new "C" body, as did Cadillac, again, their chassis design was totally different. You simply can't scramble parts like bodies and frames......at least with any degree of ease.