O.K. I'll bite, how do you differentiate between how the bottom and top sound? aren't they both mated together? And if you have heard it don't you konw whats involved guess I don't get this post sorry for sounding like an a~hole, really I'm not getting on your case, really I am not. Just don't get it...maybe that is why no one else has posted, maybe you just need to claify for us.
Just guessing but I'd say the bolt pattern, water jackets, oil galleys, and such are not the same....Like puting a 426 hemi head on a 425 Cobra Jet, won't work, and if it did some might see it as sacreligous.