Have you read Doc Dutra's old article from the Slant Six Racing News?
www.dutra.org/doug/draft-webpages/porting/ssrn-article.doc
There's also an article that talks about the newer vs older heads:
http://www.slantsix.org/articles/combustion-chamber/sl6-combustion-chamber.htm
Fourth post down on this one has some flow numbers with various mods:
http://speedtalk.com/forum/viewtopic.php?f=1&t=22094
