Looks like Z1 is jumping into the seat bracket game:
The new Z1 370Z Side Mount Seat Brackets come straight from our skunkworks facility, developed and engineered specifically for our no-compromise time attack 370Z, now available to you!
Traditionally, when installing a side mount seat in your Z you have to purchase a seat base bracket (like Corbeau or Sparco) and mount your side mount brackets to the vehicle specific seat base. Our side mount seat bracket eliminates the need for the seat base all together, reducing weight by up to 5lbs! Each bracket has a 44 position honeycomb adjuster on the front with up to 4'' of horizontal adjustment and 3'' of vertical adjustment (depending on seat).
The vehicle specific design allows you to mount the brackets directly to your side mount seats and bolt them directly to the factory mount locations on your Z's floor, reducing weight and seat height. Our brackets are compatible with most side mount that use traditional brackets. Due to the many variances in side mount seat design, we cannot guarantee fitment on all side mount seats, however we have tested these brackets on brands like Corbeau, Sparco, and OMP to verify fitment.
Product page:
LINK
For comparison, Planted/Sparco mounting requires, i believe, a $140 "base" and a $80 "side bracket"