Did you get an old kit? Those instructions are dead wrong and I believe fastbrakes has corrected this to read what it should say:
I promise you - if you go FFC customs you want the 350z brembo equipped 12.8" rotor.
If you go fastbrakes you need the 12.6" Maxima rotor.
Bought my kit last month from heeltoe, just brackets and rotors on ebay to save afew bucks.
I was about to go with
Big Brake Kit 324x30mm + Brembo ? front axle Accord VII/VIII | K-SYSTEM.pro
(if you go with them order without rotors to save on shipping since they are located in poland)
and get a brembo caliper that uses lancer pads I believe but I went cheapest route to be honest.