The stock head with the divider as I stated above had a big enough port to make over 600 HP and you only want 400 HP.
Remember the original idea of the bump port was not only to make a short side radius but to make the port smaller, Look at a stock small block chevy head at the push rod area it's not much bigger than a stock divided inline head. You measure the smallest area on a port for the air speed on a head not the largest.
This modification takes about 2-3 hrs and your done. No head bolt issues, and that was with 1.94 intake valves. No porting just a stock head with the bigger valves and dividers.
With a turbo that's all you need to make 400 HP at about 12# boost.
The turbo more than makes up for any port design, just do it, and you will be happy.
