As stated previously, it would help if you gave everyone a little bit more information to help you. What heads are you comparing them to, and what era of short block? Mark IV, or Gen V, or ....?
BTW, I run a 600 on my stock Gen V BBC with out any issue. My truck doesn't rev past 4,500-5,000 and so there is no real need for me to have more CFM. I had a 750 Quadrajet first but it didn't have the choke parts so I replaced it with the Edlebrock and I have not been able to tell the difference performance wise.
According to my research, the reason later 454s put out lower numbers is because emissions have choked the life out of them. So they typically respond well to a proper cam, one that should be in there from the factory (i.e. not so aggressive you can't drive it on the street), and also a bump in compression. If you are seeking the best HP to $$ ratio that's where I would begin looking. However, someone else might have first hand knowledge that could chime in to help you.
