Engine size recommendation

Another example I did was a 360 in my '79 Dodge Magnum. A simple bolt on part upgrades. The car was basicly 3700 lbs. The 360 got 20 mpg's. I did the following to the drive train;

360 dead stock
JY iron 4bbl intake
Carter 625 AFB MP distributor fired by a MSD 6
Dual exhaust w/ H-pipe and Thrush mufflers @ 2-1/4 to the rear bumper
The air cleaner was a factory 340 "Trap Door" w/ a K&N filter

Thae trans recieved a basic shift kit and deep pan

The rear remained stock with 2.76 gears while the car road on 235/60/15 on all 4 corners.

Headers would have helped mileage, but I never got there.

No matter which engine you build, keep it simple and mello. You will get good results and mileage from the engines. Another thing you may want to consider is an overdrive trans. The ratio of MoPars ODtrannys are .69.

.69 X 4.10 = 2.829 or 2.83 final gear ratio feel. You can accelerate quickly and shift into OD for a Hwy. gear ratio. Just food for thought.