Best magnum MPG?

75slan6,
I doubt you will ever get more than mid teens with an edelbrock carb...while they are good daily drivers, they are not known for good mpg.

I built a 70 Swinger for my son over 10 years ago when he was learning to drive, 1998 Dakota 5.2 Magnum with 42RE out of 3.9 Dakota. Swinger was 318, 904, 8 3/4 3.23 SG Power Disk, P steering, factory AC. I installed with headers, 14" K&N, 850 CFM TB, 1.7 Rockers, built FI pump in tank, used Dakota PS pump, and AC pump. Est 300HP at crank. 24-25 mpg at 80 on freeway with the AC spittin out ice cubes.

We also build Magnum powered Wranglers and I have had several TJ Wranglers with 5.2 5 speed swaps and 4.10 gears that got 20-22 on freeway. not bad for 4000 lb barn door.

If you want power and mpg, its all about injection and overdrive....you have a 5 speed so take the FI plunge, you wont be sorry you did. Many affordable options now, from factory OBD I or II system to something as simple as a FITech TB unit.