I would look into the Screaming Eagle catalog for the performance bits you are seeking first for part numbers and such. Also look into getting a stock pair of heads and find out how much to build ones up with tried and true R&D behind it. The latest PDF is in the Self Help tab above under 2012 Parts & Accessories thread...check it out!
Just because you locate ones does not mean they will be right for you...depending on how far you want to go beyond Stage II i.e. matching them to the cams, barrels and eventually the fueling and ignition mods you want to add to the "mix"! :newsmile093: