I put a 6.1 modern Hemi in my Demon, not a Hellcat by any means but the hurdles are the same. I backed it with a T60 so modified firewall, fabricated my own tunnel, fabricated my own tranny mount, changed to modern tubular k frame, utilized Holley software. PM if you want and I can let you know some of the issues I ran into. They will be similar with crate motor. PS totally worth it!