Inliners International Forums General Discussion Engines which intake to use

I have a Edelbrock SP2P intake,I am going to use with a holley-weber carb.

I have found a holley 390 cfm carb,for a reasonable price.Which I will use on a offy four barrel intake.

My question which set up would be the best to use.I want to use the set up that will give me the best fuel mileage.On my rebuilt Chevy 250 engine.

Jimmy