340 or 408?

500 hp out of a 414/416/408 is a lot easier,
I don't get this easier idea, it's gonna take a certain carb, intake, heads, cr, headers, cam etc.. For each to make 500 hp. What's so hard about getting the right parts for a 340 vs a 408 ? Doesn't take a Nascar level build to get 500 hp out of a 340 bet the parts are very similar.