Stock is closer to 48" if you measure with someone sitting on the quad. A while back someone on this site actually measured the rear of his quad after he installed 10", 4:3 offset wheels and Razr2's. He even had a picture of the tape measure, if I remember right, it was just over 50" wide. The tire itself will also add to the width, since the tire is 11" wide compared to the stock 9" wide tire.
My one 700XX is still stock width. The front has 10", 3:2 offset wheels with 23" razr's and the rear has 11", 5:2 offset wheels with 22" razr's. With me on the quad, front width is 48.5" and the rear width is 48".
Doug