Depending on the size of the engine, i and most of my friends run 2 7/16" from 350" to 434", i personally run 2 7/16" on alcohol and #18 AS nozzles as do most everone i know. I don't see any reason to run larger than 2 7/16" with 23* heads, because most of them won't flow more than 315 CFM which 2 7/16" can easly handle.
Zip.