Need recommendation for a Carb for better MPG!

if your looking for a carb to build for this project try a 6210 holley you can find on fb for 100 and take the 4brl rod off and run the primaries cause this carb you can get any jet any pump cam any power valve ect. ect. more tunable than the tq for what you want there are more variables
I don't get it, why have a 340 and detune it to become a sled? I would want my 340 to get 8 MPG and become a "Fire Breathing Animal".