To run 300zx brakes, you need the calipers, rotors, conversion brake, lines, and pads. You'll also either need to drill the Z rotor for 4-lug, or convert to 5-lug. Some early '90 NA 300ZX calipers will fit under 91 SE wheels, but the clearance is around 1.5mm! If you use TT calipers, you'll need non-stock wheels.

Here are some pics of the early '90 NA calipers under (very ugly) SE wheels.
http://www.carbonite.org/~epstein/12/DSCF0014.jpg
http://www.carbonite.org/~epstein/12/DSCF0015.jpg