I do not know much about the lsx driveline, but the older nissan sports cars have beefy trannys, all you need is a dual or triple clutch and do not have to worry about it, depending on year of the car. Most the fast skylines and 240sx and Z drag cars if standard are running OEM gearboxes and this is sub 9 second cars. The Rb is somewhat new to everyone in the united states, but people are catching on to the potental. Even the US has a low 9 second nissan running a stock rb longblock and gearbox , and irs.
Should just keep the motor in the 350z and let injected performance build it.
http://www.youtube.com/watch?v=QPys9g4diU0 street car, stock diff and tranny.