My dad used to say that Chevy tried to claim 1 HP per cubic inch back in '57. But would tell us that the 1955 C 300 had a 354 Hemi rated at 360 HP with dual quads.
These two links say that the '55 C 300 had a 355 HP 354 Hemi.... Still more than 1 HP per cubic inch, sorry Chevy....