Begin your search with this at the forefront of your mind: many dealers/some private sellers do not know the difference between the different types of 370Z, so you cannot always rely on how they are referred to in adverts. A car with a GT pack, for example, is sometimes incorrectly referred to as a GT Edition, which is something different entirely. I have also seen a Black 370Z with the GT pack referred to as a Black Edition - again incorrect. As Will says the car in the ad looks like a GT pack with the more up to date connect premium sat nav that appears in 2010+ cars.
As far as I know there is the standard coupe, GT Pack (most cars), GT Ultimate (basically GT pack with a few cosmetic extras), Black Edition (includes GT pack and cosmetic extras), GT Edition (the latest version currently on sale) and later this year/next there will be a facelift model and (hopefully) the Nismo.
Hope that helps