If you haven't seen (better yet HEARD) the OS Giken 240Z then you are in for a treat. What they did to the engine/head is an absolute masterpiece. From the speedhunters article: (link)
The numbers the motor makes in its current form are downright astonishing: 376 horsepower to the rear wheels with 281 foot-pound of torque, all the while behaving without the finicky nature you might expect from a fully-built N/A straight-six that’ll scream up to 9,000rpm and beyond. And it’s not just the power, but the way it makes it. It feels just like a 240Z should with decent mid-range punch and power that continues to build at upper RPMs. Just multiply the power and the sensations several times.