Which Carb Gives a Balance of Power & MPG?

Car & Drivetrain: 1968 B/Cuda Convertible. 318 from 1985 5th Ave. Stock, possibly Stock +1 cam, 4spd manual trans w/ 3.23 Rear End. Dual Exhaust...generally, moderately Hot-Rodded.

Currently, I'm running a Road Demon 625cfm carb. I don't know my MPG yet, as the carb has only been on for about 20 miles or so. But the power is GrEat! I did have an older Holley 600cfm carb which gave so-so power, but incredible MPG.

From my experience, I suspect that the road Demon MPG will drop.

Question: Which Carb is gonna keep the Performance & MPG at a high level?
I'm considering a Road Demon, JR (625cfm), but can't tell if it is designed to improve MPG over the Road Demon or not.

Edlebrock's seem to work well & I've gotten decent MPG & good power on my 1968 D100 P/U. Maybe that's the one? Lord knows they are a lot cheaper.

Your info is appreciated.