I wouldn't know where to buy a complete 350Z brake system, you also need to be aware that the rear calipers don't fit the Z32 without modification. Your best bet would be to buy used Z33 front calipers (or Akenobo Z34 for that matter) and combine those with 2piece 12.75 inch (same size as Z33 discs) discs. Concept Z performance sells 2piece grooved 12.75 Stoptech discs for the front which are better than the Z33 discs because those are 1piece.
I am still looking for some good 2piece rear discs myself.