truth is even on a stock ported head 217 (i assume this was Mainstreams dyno?) is still really good power. Theres very few people who crack 210 no matter what. Personally i would port the head and retune. It doesnt even have to be an aggressive port, just a street port from someone like Portflow or Max CFM will do. $500-800 tops.

should be in the upper 220s , low 230s if the head is truly what is holding it back