Hey twiggy you got none of them your model of sirio is unique to the limeted edition it is the sirio 21 wcr its almost the same as a s21pr pro but with a few major difrences. first is the liner exposed half way up the block for better cooling and weight saving its called integral aac liner. You should be able to see were the liner fins start and the crank case ends. It uses a 6 bolt config to hold the head down and 4 bolts to hold the liner inplace. by the way those 4 bolts under the head are imperial size not metric. don't use a 3mm hex key i think if i rember corectly its 2/32" of an inch hex key you need all the rest are metric. It also has a black hard smooth coating on the crank to prevent ware + the crank is dubble blanced. the stats for that engine are way up there with even the top engines now. collari won the 2003 worlds with that type of engine and then won agen in 2005 but with the gold head collari edition of the engine. Get a 2013 rb or sirio pipe and conical header to make even more power. Its very smooth power and out of this world rpms. just keep checking the bearings as the rpms the sirio engines pull is very hard on them. Best Regards Jeremy.