The North to South R2R record was broken 5/27/2011 by Jared Scott. He clocked a 3:06:10, as reported by Caleb Schiff. Scott's time beats Allyn Cureton's 30-year-old record by 37 seconds!
Some additional info posted to Facebook:
So just to be clear. Jared Scott ran a 3:06:10. Jason Wolfe was feeling strong and making up time on his way up S. Kaibab but got stuck behind a mule train. I believe he would have had it too if not for the asses. His final time was 3:13 and change.