wheel spacers spacing

I have done exhaustive searching and cannot seem to find the answers to two simple questions. 2008 Tahoe Z71 4X4 Stock Wheels (18") and Tires, Leveling Kit - 2.5F, 1.5R 1) Do the front tires sit a bit wider than rear tires, like in some previous generations? If so, by how much? 2) What...