You refering to dirt track racing correct?
I do know that most stock type classes stipulate stock heads or at least stock "appearing" and stock valve locationing.
I've known some who will have their heads ported but with a abrassive media rather the typical grinding assoiciated with porting that looks so obvious, its stock appearing and they are getting some pretty good flow numbers out of stock "APPEARING" heads. Also they'll use it on the manifold as well.
Its called extrude honing.
Look into it.