The sixth generation of Buick’s Roadmaster flagship launched as a 1954 model. The chassis was lowered and widened relative to its predecessor, and handling was greatly improved. Under the hood, a new 322-cubic-inch V-8 engine replaced the long-running Fireball straight-eight. Redesigned bodywork was more streamlined, and while the exterior of the Roadmaster was largely the same as that of lesser models in the lineup, it did have four fender-mounted “ventiports”—one more than usual—among other subtle cues, to help…