The 8.1L will bolt to GM transmissions like the TH400, SM465, and 4L80E. You can reuse those if they are already in your truck. We had the 4L80E gone through by Gearstar since the company can build automatic transmissions to live with very high horsepower and torque. Our build was pretty mild considering Gearstar’s options, but it will be adequate since our axles will have very deep 6.84 gears. Because our engine and transmission came together from the factory, no special adapters or unique flexplates were required.