Bowser

From Bowser website

Model 55460: The 50 ft PRR cars were built in 1936 as Class X32A round roof automobile boxcars, rebuilt to PRR 131000-131094 Class K9 (single deck), PRR 130000-130103 Class K9A (double deck), and 131050-131299 Class K9B (single deck) starting in 1959. Variations in the ventilation hole pattern exist - be sure to work from prototype photos. Wabash had similar cars (WAB 16600-16615) rebuilt in 1963 but with a single door and a different ventilation hole pattern.

From Bowser Website

Bowser's 55450 series kits represent PRR 130501-130554, Class K11, double deck stockcars rebuilt from Class X31B automobile parts boxcars in early 1961. See Richard Burg's The Last Stand of Stock Cars in the East in the January 1993 RMC.