you know what you are right , they are like night and day ,,,,, have some fun with the 400 but ill tell you this you will never look back to the small block ever again once you go big , all your ganna wanna do is go bigger and bigger , next thing you know your ordering a stroker kit from 440source for that 400 and bam you have a 500 stroker with their alum heads and the cam setup , you will never ever look back to the small block stage with that kind of power