Edelbrock Performer on a 318?

Hi guys,

I have a '70 Dart with a 318 in it. I'd like it to be my daily when I'm finished working on it, so of course I'd like to improve MPG if possible. I've done my research and found that the best way to do this is let her breathe easier, open up the headers, the exhaust, and all that jazz. I've also seen one guy who says a conservative 4-barrel will improve my gas mileage, but I'm not sure I buy it. Best recommendations I can find for a 4-barrel is the Edelbrock Performer, the 500 cfm model. I think my stock Carter 2-barrel is running about 250 cfm... would I see an increase in MPG's with the new carb, or would I just make her suck down more fuel?

Thanks for any responses.

Jim