Best magnum MPG?

RustyRatRod said

I know it's not a Magnum, but the LA 360 in the 71 Dart I had years ago did 20 on the highway with 3.23 gears. It had a Thermoquad.

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So in my 72 Duster with a 3.23 rearend, 1406 edlebrock and an overdrive 5 speed I should easily hit 20+? I'm hoping for 25+ on the highway but 20+ would be great too!