I had that model quoted using a sand printing mold/casting company and it was a fair bit but it will never be a cheap project if I ever do it anyway. Beauty of it is any changes to the design can be easily tweaked for the second or third casting etc. Investment casting is another option too. The water gallery is near impossible to pull a pattern off and sand printing or investment casting takes care of that.

As for making a billet head with water jackets I have no idea how you would tackle it all. Have looked into it a few years ago but seems near impossible to remove enough material from above the combustion chamber. A lot of the billet heads I came across for drag engines on methanol.

The twin cam head is pretty awesome engineering feat for sure but its no AY12 replica