An interlocking body and floor pan assembly for a below-floor energy stored vehicle includes a vehicle structural assembly having a front compartment section connected to a rear compartment section using first and second rocker members. The front compartment section includes a compartment front cross-beam and the rear compartment section includes a compartment rear cross-beam oriented parallel to the compartment front cross-beam. The vehicle structural assembly defines a bucket configuration having faces of the compartment front cross-beam and the compartment rear cross-beam angularly oriented from an upper outboard edge downwardly pitching to a lower inboard edge. A prefabricated sub-floor assembly seats on flange structure and is positioned with a clearance to the bucket configuration of the vehicle structural assembly. An outer perimeter of the sub-floor assembly is larger than an inner perimeter of the vehicle structural assembly where the sub-floor assembly contacts the vehicle structural assembly.