A 600 is sized pretty close to ideal for a 350 CI engine. I don't know if less cfms would reduce gas consumption or not. Gastrick put trips on his Deuce recently and says the gas milage has improved over a single four barrel because of running on the smaller two barrel, so maybe.

You might have it put on a scope to see what your air/ mixture is and all that stuff. I had that done to a 351 Cleveland I had one time and it really told us a lot about what was going on in each cylinder.

Don