LA means light A motor, designation given when it was redesigned to save weight. stock 340 block survives up to 450-475 horsepower well, after that you are looking for trouble. it is a passenger car motor designed for street use not racing. that's why they started coming out with race blocks. and I guarantee with todays stick tires and track prep you are looking for trouble past 500hp. even if its occasional trips to the drag strip. and as horsepower goes up you are looking at freshening the motor to keep it performing consistent for racing. kiss the valves, rehone the cylinders, maybe replace the rings and check the bearings etc.. performance falls off faster than you would think and everyone I know races to win.