I tried doing the 300zx Brake upgrade on my B15 SE. The calipers bolted right up, but there are major clearance issues. Even with my aftermarket 40mm offset wheels, I STILL needed more clearance. This would mean wheel spacers, and possibly longer Nismo studs.
You also need to resize, and redril the 300zx rotors, not to mention getting custom brake lines. What looked to be a "budget" brake upgrade, soon turned into a 1,000 dollar nightmare.
I know SMC was looking into making a "kit", but I don't know what the current status of that is.