Just make sure that they are the correct ones to suit the 350Z then. They make a lot of fan kits for various vehicles as well as some "universal" ones but if you get the wrong ones then obviously they either won't fit or won't work as well as they should.
Little bit of fitting info here: http://www.350z-uk.com/topic/72351-has-anyone-fitted-a-mishimoto-nissan-350z-aluminium-fan-shroud-kit/