The 1956 300B was fairly similar externally, distinguished by a new tailfin treatment, but with larger engines, two models of 354 cu in (5.8 L) Hemi V8 with either 340 or 355 hp (254 or 265 kW). A total of 1,102 were sold. Performance was a little better than the previous year's, being measured at almost 140 mph (225 km/h). A 6.17 ratio rear end was also added to the options. Front leg room was 44.6 inches. New was the Highway Hi-Fi phonograph player.
With the optional 355 hp (265 kW) 354 cu in (5.8 L) engine, the 300B became the first American car to produce 1 horsepower per cubic inch, besting Chevrolet with their fuel-injected 283 cu in (4.6 L) by one year.