Want to put a magnum 5.9 in my 70 dart.

Hello, first post so be gentle on me . I have searched but not finding the info I am looking for.

I have 1970 dart swinger that I want to put a magnum 5.9 in with what transmission I am not sure of yet. What's my best/ least amount of cutting and welding needed for this swap.

I have the conversation mounts for the engine.