As Kas Kastner, one of America's legendary road racing team managers says, "The rule book is grist for the thinking man".
Actually the biggest gains over the last 7 odd years have been in camshaft technology, at least in the old crocks we race. It's all in the ramps. A true black art. All I know is the valve acceleration with these new grinds has forced everyone that uses them to dramatically increase the strength of the rocker shaft assembly.
Oddly, much of what has been done is a result of studying modern variable valve timing set ups, and a very close look at modern motorcycle practice, as far as cam profiles go.
Cheers.