Manton has a Faceboogie page and they say they use tool steel for almost everything. They don't say which tool steel or what the heat treatment/hardness they have. I suspect it's A2, but I haven't been able to squeeze anymore info out of them. I've heard the Jesel SS rocker arm kit is about $6k and there is three or more versions of them.
Any part for Hemiroid motor is never cheap, good parts costs a lot more money than the cheaper ones, but you may save money in the long run by buying the good ones to start with: up: work:
