ok well boreing and strokeing is a good start getting the comp up is also good if poss then larger valve area and a well matched cam and it all balanced and flowed for said setup then maping also cooling and oil pressure and flow poss needs looking at ,not sure if your get your target bhp but you can get a lot out of NA engines ,do have a lot of talks with people that have already maxed out this engine as they will have done most of the hard work for you in finding what works .