Need recommendation for a Carb for better MPG!

I can't see why that isn't possible as I have a 410 in an A body .
Trick Flow heads, 11 to 1 comp forged pistons and crank, 238/242 @ 50 with 610 lift and 3.91 diff ratio and on a recent trip of 600klms (about 370 miles) I got 23mpg.
It is a 5 speed manual with 28 inch tyres and does 110kph(75mph) at 2400 rpm.
Yes I know our imperial gallon is slightly larger than your US gallon but my 318 auto charger that was in convoy with me only achieved 18 mpg and it is a low milage survivor car with about 55000 miles on it and is 51 years young.
With a proper tune and a decent ignition system those numbers are achievable!