Factory HEMI Head!

3D CAD
Billet Aluminum (not enough volume for castings)
5 axis CNC
DOHC
Modern chambers NOT necessarily Hemi
3.62 or shorter Stroke
Zero deck
Belt Drive cams
Off the shelf rockers
Crank trigger
Dry intake EFI
External oil pump

…and a pony! No, two ponies! And $50bn in untraceable bills! And a bottomless bucket of really good southern fried chicken! And…

You will have to commit to doing this with the mindset it won't make You a dime

In fact, it will wind up costing you a very, very, very large mountain of dimes.