318 heads

LOL! Well, the increased torque is always welcomed and run for sure. It would be the main focus I think for getting the most out of the fuel for mileage. A&F easy in, easy out, all burnt up, yea, winner I think.

On my first ‘79 Magnum with a 360, I was able to get 20 mpg on the Hwy. Now I can get a good bit more out of my ‘15-1500 Ram.

Using basic mileage techniques, IMO, I did pretty OK.
A nice mileage getter was the MSD & a .055 plug gap at a low cruise speed for the multi spark advantage. Other than that, I used a 600 AFB on the factory intake with a trap door air cleaner. Dual exhaust off of the manifolds. 2.76 gears behind the 904. And easy on the Hwy speed.
I never got to headers, which may have helped. IDK though, maybe?
Yup. I think headers help mileage every single time. But you have to remember to get mileage, you gotta govern that right foot.