Magnum VS Hemi

This is a good read. I have a 5.9 300hp crate motor that I pulled from a 71 Cuda. Found a correct 71 340 for the Cuda. Customers car. He sold me the 5.9 for 1000 and it probably doesn't have 200-300 miles on it. I drove it before I pulled it and it ran great. Could not pass it up so it's going in my 72 Dart with a 4-sp. It came with the flywheel, intake and oil pan which just sweetened the deal. Want to find a bigger cam and maybe some aluminum heads. Would like to get it up to around 400hp. Was going to slam a 440 in the dart but this sounds like a better plan.