How can you get your hemi over 400hp?

To get your HEMI engine over 400 horsepower, consider upgrading the intake and exhaust systems for better airflow, installing a high-performance camshaft, and tuning the engine with a quality ECU remap. Additionally, forced induction options like superchargers or turbochargers can significantly boost power output. Ensure you also enhance the fuel system to support increased performance. Lastly, consider strengthening internal components if you're pushing the limits of the engine.