If you have a built motor on stock suspension, you won't be able to put that extra power to the ground. Fortunately, Ohlins has you covered with their fully adjustable, high-performance rear shock for your Softail.
The S46 rear shock has been designed specifically for the M8 Softail platform and offers a large 46mm main piston, an internal gas reservoir hidden inside the main body of the shock, length adjustability, and a hydraulic preload adjuster. With adjustable damping, you can change the behavior of the shock to suit your taste.
The tool-free hydraulic preload knob allows you to make incremental adjustments completely separate from the mechanical preload on the spring, perfect for unexpected passengers!
 
Is An Aftermarket Shock Worth It? | The Shop Manual
The Indian Larry Twisted Frame Chopper | J&P Custom Motorcycle Builds
150-Horsepower Harley-Davidson | J&P: Custom Motorcycle Builds
124 Cubic Inch Twin Cam FXR | J&P: Custom Motorcycle Builds
The First 8 Things You Should Change When Buying a Harley Davidson