There is no naturally aspirated recipe. Well.......where it would still be driveable on the street. You'd be talking about above 12.5:1 compression, BIG custom solid roller camshaft, all out ported head with huge valves, a large four barrel and big tube custom headers. Then you might get to or slightly eclipse 300 HP.
It's all the head. The 170 was designed first. The head was designed around the 170 and never redesigned around the 225.
