Since it's down this far,,,,,,,,,,,,,I'd have to upgrade the camshaft and springs.Something like the Howards 340 horse 409 replacement grind would really wake that otherwise stock engine up.If you are pulling the heads,check if they have the stock valves in there,and if so,replace them,at the least the exhaust,with stainless valves for two reasons.I.The stock valves are 2 piece and subject to break.2,The exhaust valve is not compateble with todays unleaded fuel.