Erik has the right idea, when it comes to carbs and engines, bigger is not always better. Nor will a bigger carb make more power.......With that said, I suggest a 600cfm Holley double pumper, after that find yourself someone with a chassis dyno that offers carb tuning services and have them spend an hour or two properly tuning the carb to the engine. I'll bet that you'll make more power with the holley 600 than your old carb, not to mention you'll have better (read this as crisp) throttle response to boot..........

Bill S.