MPG Motor Magnum vs. Hemi

Thanks for all the suggestions. It’s a pretty tough decision. I love the 413 and push button, but I just feel it would be tough to get the mileage up in to the mid-high teens? Tires will probably stay 14’s with factory 3.23 gears. I can get a 5.7 hemi here locally complete for $1500. Magnums can be had around $500. Then the cost of the fuel and computer system . I will look more into the gear vendors as well.