What would be the easiest 5.9 Magnum engine and auto transmission combo to swap into a 66 or 67 B body that originally was a poly 318 A engine with TF auto, column shift?

A company close to me has many different engines reasonably priced with wire harness and computer as a package deal.

Many with reasonable miles and I'd like to upgrade and give this combo a try. The more bang for the buck the better. Any and all advise and suggestions are appreciated.