Its a sweet link for anyone looking to buy heads or if you want to have a rough estimate of what your heads flow.... Thers is LOTS of info on there....they have stock numbers for most heads (stock and aftermarket) and for some heads they have numbers for stage 1, 2 and 3! its a sweet link, check it out
http://www.jason.fletcher.net/tech/flowdata/castiron.htm
http://www.jason.fletcher.net/tech/flowdata/castiron.htm