Holley street Avenger. I think they make a 600 cfm avenger. Has all the hookups and emissions ports aaand, even has the AOD tv bracket already in place. Nice vacuum secondary carb for good milage and throttle response.
Get a fresh one. You want to know that for whatever reason it is not working after the conversion, the issue is not the carb. You dont want to debug a carb as well as the conversion.