Invaluable info here, so I guess that the ideal solution is to just get whatever V8 722.6 OE combination is available, prefer a 6 liter NA engine though. What they are should be available on Wiki or somewhere.This is not a project that I'm jumping in today but at least the powertrain search can begin.

Third generation Mopar Hemi. MB M119, M113

That's an option I hadn't considered, iron block is a bit of a negative weight wise, will check power output.