If you need a better quesstimate, please add in the cam specs, how much shaved off the heads, how much port work, size of valves, type of pistons such as flat tops/12-1 compression etc., any work done to the intake? any work done to the carb?...is it gas or alky? I myself havent worked with small block chevys since i quit dirt track racing about 9 years ago and went drag racing with a BBF. But i am sure that there are alot of smart guys on here that would like to help you out if you gave them the info needed.