318 to stock 340 power level questions.

Have the heads rebuilt with performance in mind. Meaning 1.88/1.60 valves and a 5 angle valve job. Have them milled .030 on the decks and intake surfaces. Cut the spring seats for dual springs, and then stick a modern cam like the 268 series Lunati or XE Comp and you will be at the 300hp level thru the manifolds. Peice of cake. If you find int needs pistons, stick in some hyper flat tops with valve reliefs and you'rea cam change away from more power later.