440

440 with flat top pistons, 240 TF heads, TF intake and a good 850 carb should be 600 hp without too much trouble. A moderate flat tappet cam should get you there. Lots of cams to choose from but even an old school cam like the MP .557 or the MP .590 would make plenty of power with the TF heads. Or just call any of the cam folks and order something custom.