headers or manifold?

master plan here- 360ci (904 or 727 trans, if it help) in my 70 dart. daily driver with some fun power an good mileage. my question is what would be the most sensible route for my application?

headers or manifolds? ive read that 340 manifolds are good stock but are really expensive and i dont have a cash tree.

any suggestions? all i know for sure is im goin to do true duals with turbo mufflers.