In this video Rich Froning does Grace with 225lbs. Grace is normally done with 135lbs, so Rich stepped up the weight a bit and still finished in 4:49.
This video is from 2011, but it is still the fastest CrossFit Grace time I can currently find. Rich Froning also has a listed Grace time of 1:11. Nate Schrader has a 1:04 listed Grace time, but no video..