I've seen a few articles in Hot Rod type magazines that freshen up the old motor home 440. And they use the cast crank and the smog heads. The power adder was cam, springs, and headers. The power output was quite remarkable for just what they did. You can use the trans from the motor home and motor mounts can be bought that make it a bolt in with the K-member you currently have in your Challenger. If you want to boost power a little more, bore the motor 30 over and up the compression to 10 to 1. That will put you over 400 HP at the crank. And from what I've read, the crank holds up quite nicely. So go for it and make it what you want it to be. Good luck.