Just to add a bit of information...I was reading another thread on spindle pins awhile back (can't find it now) that mentioned shear strength of bolts and if there was risk of failure using Grade 5 or 8 hardware (the 10"x5/8" replacements that others are talking about above) instead of stock or MSA hardware:
The shear strength of this particular bolt:
91000*Pi*(5/16)^2 = 27,000 lbs
91K is lbs/sq in of shear strength. 5/16 is radius of 5/8 bolt.
Seeing as the load on this bolt is fairly direct in line with the force (right inside the tire) and not being multiplied by some greater ratio, I'm no longer worried about using a $10 bolt and nut from the hardware store