this is where knowing the properties of metal come in hand, and I know, that Jeff, being and engineer, knows what certain heat treating procedures are for. A grade 5 bolt is strong, has a good tensile, and compressing strength, and the same time, not becomming brittle, allowing it to bend if it takes a good hit. a grade 8 is real strong, tensile and compress. but the down fall of a grade 8 is that if you hit it hard enough, not saying that it is likely with a truck like this, is that the bolt will shear, without warning but that will take a real good hit. I'd rather use the grade 5s in suspension for that reason