Most everyone on this site will suggest a properly tuned/rebuilt original quadrajet, I'm sure. That's probably the best choice. I understand CFM doesn't matter as much on those. Personally, I have a Holley 600 CFM vacuum secondary, and I'm very happy with it. You don't want any Holley bigger than a 600 on your 350, trust me. I think you already found that out. Also, I believe that the edelbrock carbs are based on the quadrajets, you may also be able to decrease the jets or something like that, and keep the carb you have. I'll defer that question to someone more knowledgable.
