IF you are sticking with a two barrel setup the 500 2v Holley carb would be a safe way to go. Anything over say 5500r would definitely need a 4v. Edelbrick 600 is doable to about 6000 but it all is subjective of your ve% and where you want to run

 

The Summit M2008 600cfm is a great carb built on the original autolite design, and the annular fuel boosters are no joke!

 

ok, old thread and others might be fighting this problem and i may have missed it throughout this thread but, the float could be bad (as in taking on fuel). the carb will always be asking for fuel. a new float may be in order in this situation.