I'd like to get the best mileage I can. I know that in speaking of muscle cars, mileage is usually not a concern but I am not concerned with how fast I can go anymore. I'm planning on changing the rear gear to a 3.23 from the current 3.91 that is in it and thought a smaller carb. would help as well as long as it won't affect how well the engine runs (not speedwise but just general operating performance). What I have is a pretty much stock 67 440 HP engine except that when the previous owner rebuilt it, he installed lower compression pistons. I don't know exactly what the ratio is but I think it is about 9:1 or thereabouts based on what he told me. The engine currently has a 750 Edelbrock 1411 carb on it and I'd like to replace it with a lower cfm carb. if possible. Would a carb in the 600-650 cfm range be enough carburation or would that be too small for my 440?