havent really thought about it, im looking for about 600hp out of the 427 thats why i think that the more expensive manifold will work better for the 427, do you have any head reccomnedations, right now im looking for a good 427 block to build, this 427 is gonna take me forever to build b/c of my budget, i looked at the blue thunder heads but they seem to have way to big of combustion chambers, i dont know if that will be to great for compression