The 12 port head is also custom.
Not really, custom hints at a one off concept, and all the 12 Port head components are production parts and not one off's, and are sitting on a shelf waiting for you to buy them. They have been figured out and proven for over 30 years, and is "store bought", as are the other components required to use it. The cost to purchase a set of V8 heads that are even capable of out flowing and out performing the 12 Port head to begin with will cost more than buying a 12 Port head($3500 fully ported), then you have to saw them apart and reconfigure them to re-weld them. Do you want to saw up a set of heads you have $3500+ invested in? If your truly wanting to mimic the performance you mentioned, that is just the starting point and you haven't begun to prep the shortblock to handle that kind of power output, which will easily cost as much or more than the heads will cost.
