mshred,
I respect and appreciate you at a young age asking all of these well-thought out questions.
A very wise engine builder named Joe Sherman once said "$1 in the heads is worth $3 in the shortblock." I've found this to be more true than you know, don't sweat it there's plenty of 408-416's out there that crush big blocks all day long.
My
build the best nicest forged 408 you can afford to build and enjoy it! Take what you learn from the experience of building it and look forward to rolling that knowledge in to the next one, pretty much what I've been doing for 30-odd years now