B&M's Automatic Transmission Input Shafts are available for GM Powerglide transmission in a GM Turbo spline configuration. These shafts come in 3 different series: Maraging: The choice for engines producing up to 1,200 horsepower. p300M: Excellent choice for ratings up to 1,000 horsepower. Hy-Tuff: Excellent choice for engines producing up to 800 horsepower.