Look here for all the details ..
NISMO | VQ35DE Engine Parts
The heads were used on the NISMO RS380 Type C - the 350Z JDM race car in Japan.
I'm still trying to get to the bottom of the engine spec used in the PlayStation GT4 370Z's that ran in the Dubai 24-hour recently, but I suspect these engines either have these heads (the Spec 2) or they are fitted with 370Z heads that have been modified to remove the VVEL arrangement.
My guess is the reference at the top of this post is to the NISMO heads which will flow to 440hp (but the standard inlet manifolding only runs to 420hp - to get 440HP you need a modified inlet manifold).
I have a set of 6 x 52mm throttle bodies that we've dummied up to a HR head off a 350Z engine that was detonated a few years ago, and we are playing with airflow (valves sizes, angles etc) to se how much flow we can get (NA-only). The manifold is built up from Ali plate and tube but is internally polished ...