The engine would need to be fairly well sorted out to make 750 hp with the 240 heads. It can be done and it would be a screamer but you would need to have your act together to make it happen. Cam, carb, intake, etc all need to be correct.

How much compression are you willing to run? If you are willing to run race gas then building the engine at 13:1 makes it a lot easier to make the power number. You can do it with pump gas but the combo would need to be super well dialed in.