I think the engine is the only fifference :
The Powermaster was a full-size car, offered in pillared two and four-door sedan and station wagon models, and powered by Chrysler's 251 in³ I6 engine. For both of its years in production, the Powermaster was available as an eight passenger sedan through the use of jump seats. The Powermaster was also built on a longer wheelbase (139.5 in (3543 mm)) than regular six-passenger DeSotos (125.5 in (3188 mm)). A version of the long wheelbase model was used as a basis for the DeSoto Taxi, seen in many Hollywood movies from the late 1930s through the mid-1950s.
Chrysler of Canada built the DeSoto Powermaster in both 4-door sedan and 2-door hardtop body styles, the latter not offered in the United States. The Canadian DeSoto Powermaster also used Chrysler's 265 in³ flahead I6, an engine that first appeared in the 1952 Chrysler Windsor.
The Powermaster was dropped at the beginning of the 1955 model year, when DeSoto transitioned all of its automotive models to V8 engines
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