Pair Polyurethane Motor Mounts Engine For Small Big Block Chevy SBC BBC 350 454. For Small & Big Block Chevy SBC BBC 350 454. Heavy duty motor mounts made of steel with polyurethane cushions. Ideal replacement for original GM Motor Mounts.Polyurethane with zinc plated steel construction. Reinforcement plates includes for extra height and strength if needed. Two motor mounts & two backing plates. Professional Installation is Highly Recommended (No Instruction Included).