I think my father had Buick Roadmaster. It was not white and not a convertible, however. Would have been around 1955, I think. His was blue. I remember that it had “dynaflo” —if I remember the word correctly —whatever that is. I’m a woman, and not a car person. (But I can appreciate the beauty of the car in the picture that you posted.)
Yes, Dynaflow, it was Buick’s first auto transmission, a reliable unit, but Buicks equipped with this transmission were gas hogs, they only got 12-13 mpg.