It seems to me you have missed a number of Buick sedans from 1948 on into the 1980s. Some were square brick shapes with portholes (1953) but there were also a number of "fastback" models that were really swoopy. See if you can find a history of Buicks with pictures, I think they had more fastback models than any other brand. I am trying to remember the more recent models but they were really swoopy and WIDE.

Don Shillady
Retired Scientist/teen rodder