I will be upgrading the Tea Pot Carb and Load-A-Matic Distributor on my 55 Bird.   I will be installing a 1957 distributor with a Pertronix unit.  I have a set of reconditioned 1957 G Heads and an iron 1957 Ford Holley pattern intake also.  I need to purchase a Holley Carb for this intake.  I am thinking about buying a new 600 cfm Holley with vacuum secondaries.  I see on this forum where some of you are running a 450 cfm carb.   My engine is stock, but I probably will want to build a mildly modified engine in the future.  Is there any advantage or disadvantage to purchasing a 600 cfm Holley?