Hi mate, I have a TT 350z and have done a fair (HUGE LOL) amount of research in the 350z with FI and the GT35r is a fine turbo mate, you can run safe at 4-6psi on a OEM motor for a while and then turn up to 15+psi when built.
If your building the bottom end Id say go for a billet 35r or 37r with a decent size hot side. Lags not much of an issue with 3.5L motor, Honda s2000 run gt35r's on a 2L motor!
Dont just look at garrett mate, check out borg warner and precision as they my have a decent option too
Have fun!
Ps. Try not to get boost hungry and blow your OEM bottom end so run light springs in the wastegate till your built. If you have any overboost problems you may end up losing the motor and your shiny new turbo too