I'm assuming you are not worried about looking stock since you are talking about the Holley Avenger. But, I'd seriously look at the Barry Grant Demon carb. They make a 625 cfm model for the street that has all the advantages of the Avenger and is $299 at Summit if I recall.
The Ford may be a little more expensive because of the kickdown linkage.
By all account, the Demon's outperform the Holley's.
Check out
http://www.demoncarbs.com
I just bought a Demon for another car. I had to send it back and ironically I bought a 770/870 Avenger instead. The reason was I really needed a choke and to maintain the factory linkage. The Demon I had did not have a choke, did not fit my stock linkage and the I need to get another fitting for the duel fuel line.
If Demon made a street carb > 650 cfm (like a 750) I would have bought that in a heartbeat. The Holley Avenger was made to compete with stuff like the Demon, Bill Mitchell, etc. because they were taking Holley's market away for a top-quality, high-tech engineered carb.
