The OEM bolts are a bit different than the common hardware store bolts as in they have a wider than normal shoulder that extends down through the brackets. Although any bolt will do, if not the correct fit, the vibration and movement will elongate the holes and the rack will rattle a lot. Body stress cracks could also form as a result of the rack moving around.
After 200 thousand miles, mine was loose and the holes slightly ovaled, I redrilled one size up and used a set of bolts out of a YJ that had the shoulder length I needed. Then I measured and cut off the extra.
New bolt before I cut it.