Look in the inlet bell if it is a 49 it will be the same size as the hole on the inlet.If it is stock it will not be as big as the inlet.Believe me I was told the same thing and got shafted for a stock turbo with a inlet bell on it.Notice on this pic the blades fill out the hole on a stock turbo the blades won't fill out the hole.
stock turbo intake wheel has 7 blades and they have one tall blade and one small blade side by side for a total of 14 blades and the ta49 has 6 blades and they have even size blades next to each other for a total of 12 blades