a friend of mine is using blue thunder heads on his 427 he is shooting for about 800hp i was told that the blue thunder heads have huge combustion chambers that make compression on the low side but other than that from what i hear they are great heads, edelbrock heads for the FE are decent too but im not sure if they would be able to attain numbers like 800hp if im wrong someone correct me on this, i have a set of 406 heads on my motor right now they are off of an original 2X3 406 galaxie they flow pretty good but would never be able to get in the 800range they might be good for maybe 500hp