Into the weeds engine design for fuel efficiency discussion.

Have you considered the 3.6 pentastar? Pick-n-pull maybe? The more I learn about it the more I like it.
Personnally I am not a fan of the Pentaturd. Took one look when they first came out and I was a mechanic at a Dodge Jeep dealer, and decided I did not like it. Your results may differ, and that is OK. The old faithful 318/360 are readily available, so they are relatively inexpensive. Real easy to work on, while the Pentaturd with its DOHC and VVT can be a nightmare. The wiring would be a PITA.