This is interesting because I recently was looking at some 2009 x-drives and they looked the same as the i versions. I just assumed that was the case because of the different rims (the 08 coupe ones) that I wasn't used to.
I don't have a 2008 3-series brochure but i have a 2009. The only place where any dimensions are shown is the 2nd to last page that has a graphic of the front, side, top, and back of the car. There is only one set of dimensions shown.