Those things are killer. I love those heads. For the money, for a 23 degree low port head, they make serious power, worked up properly. Even just mildly done, they will make good power.
They do use an off-set rocker though, which is one of the advantages of them. I wouln't buy complete heads, from a certain big mail order house in Wisconsin though. Trust me. If you want .010 run out valve seats, and cheap parts, then fine.
Frank
Advanced Performance
www.get-ap.com