New Engine

Would anyone know where would be the best place to purchase a remanufactured hiperformance replacement for a 440 magnum for a decent price. This is my very first ever project with a mopar and it s a 70 cuda 440 magnum. Like to put away the original motor and go with something much stronger for driving around since the original engine is kinda tired and don t want to push it. Also, does anyone recommend the marine engines as far as durability at all?
I would highly appreciate any help I can get in this matter. Thank you all. :notworth:
Bob.B