I ran a holley 3310 with a pro form main body on a 7.5:1 318 with 360 heads and an air gap intake. It would roast the tires from a slow roll, ran good when rpm'ing, and got 20+ mpg. The carb aint too big, to reiterate from whats been said it just needs to be tuned, those carbs dont flow what thartre "rated" at