I would go with the Edelbrock 750. Double pumpers were always to much carb for street use. I run a 750 Edelbrock with an electric choke on my 454HO. It's a 454HO crate engine Gen VI four-bolt big-block, forged steel crank, forged connecting rods, and forged pistons, roller camshaft Camshaft duration (@.050 in) 211 degree intake / 230 degree exhaust with .510/.540" lift. Cast iron cylinder heads, rectangular port, 118 cc chambers deliver a pump-gas friendly 8.75:1 compression ratio. 2.5" American Thunder Flowmaster Exhaust with Hooker headers. Horsepower comes in at 425 with 500 lb.-ft. of big-block torque.

In a 72 Chevelle with a 700R4 and 3.73 posi rear it gets 15-17 mpg on the highway.