Superbees came standard with 383's and you could option 440 or Hemi...
R/T came standard with 440 and optional Hemi...
I believe the Superbee was the sister to the Roadrunner and started as a basic B-body with cheap interior and a 383 so the working man could drive it to work during the week and then take it to the drag strip on weekends. Cheap, affordable, hot rod and family car....