I agree Gr 5 is plenty good but if you want Gr 8, I understand. If they break, it's time to get stronger. Be sure, as Sput is saying, that something is not wrong with assembly or another part which is over-stressing this bolt. It does not seam like it is under much load, but I'm not sure. If the plates are not bent after bolt breaks and they are not shifting, one up and one down, then I don't see any stress. Where exactly do the bolts break? Middle? head? nut end? strip? Are the holes in the plates for this draw bolt oblonged? If it's 3/8 bolt it has 1000's of lbs strength. Somethings up. 307A= 60KSI= 60,000PSI. Gr 5= 120,000PSI, Gr 8= 150,000psi as a comparison. Caution: Bolts must be torqued to specs or they may be subject to early failure in some cases. Many online bolts will be Chinese also. It is possible that off shore fasteners do NOT comply with the specs and/or are not made/tempered properly. Are you jumping ramps at car shows? Are you a moonshiner?
