I think Nissan has done a much better job on the 370Z in insulating the noise and vibration compared to the 350Z.
Anyway, I marked up on the OEM stick where I think it's rubber and where a lot of the slop is coming from. See attached image below.
Compare that to the B&M unit, you can see in this image:
The "brass" colored part in the pivot point is indeed a brass bearing encased in a stainless steel bearing case. I think the reason why brass is used is that the material can be impregnated with lubricant and as the bearing gets used more it releases lubricant to smooth out the shifting, but retain the tight tolerances and precise mechanical feeling metal bearing gives you. You can't see it from this same angle, but the top stick is installed over the lower stick like a sleeve with a hard rubber material as the noise insulator sandwiched between the two stick, then bolted down to prevent any unwanted movement.
If I can get 10 confirmed orders I can probably work something out as a pretty significant discount. Add your name to this thread and when we reach 10 I'll see what I can do. Group buy detail will be emailed to each participant when I work out the details.