Need recommendation for a Carb for better MPG!

Way back in the late '70's, I put a 318 cam in my 340 with 10:1 compression, an SP2P manifold and the original 4425S Carter AVS. with 2.94 gears and 27" tall tires, I got 22-24 MPG. The car is as shown, a '68 Barracuda FB FS. I did convert to a desert cooler radiator and a 14" Flex-a-lite electric fan to eliminate that power draw. Never overheated in 117°F heat on a drive to Tuscon from Orange County. Once drove it from South SF to Irvine on one tank of gas. On fumes when I got there, but made it. About 380 miles on 16 gal. I wish i never changed from that configuration.