1955-1985 Small and Big Block Chevrolet including 348-409, 6061 T-6 w/1045 steel friction plate, Internal Balance, 14 LB, 168-tooth;SFI-approved – legal for use in racing classes that require SFI certification; Choose precision CNC-machined 1045 billet steel for maximum strength and durability or 6061-T6 billet aluminum construction for weight reduction and excellent heat dissipation; CAD designed to provide optimum performance and reliability;