Phil- - - -without some sort of confirmation from the engineer who specified the bolts for that application, it would be difficult to determine what grade of bolts were used. You might have to dig him up and ask. Good luck with that! Are there any identifying marks on the bolt heads? Usually a Grade 8 has six lines on the bolt head, while a Grade 5 only has three. The bolts without any ID marks that are found in bulk bins at hardware stores are usually Grade 2, and aren't really intended for automotive use. I'm sure there are a lot of them running around on stovebolts and other vehicles, however. I'd be a little reluctant to use a Grade 2 bolt in a high-stress area like a steering system, however.

Vol- - - -in the case of a spindle nut, there is a little wiggle room on bearing preload, and the cotter pin is used as a mechanical locking device. Later model spindle nuts have a sheet metal lock collar with a lot more choices for positioning, so an accurate preload can be done with an inch-pound torque wrench and the nut doesn't need to be backed off. On GM cars from the 1970's and later, I believe the torque spec. is 72 inch-pounds. That's for tapered roller bearings- - - - -on early stovebolts with ball bearings the "torque and back off" method seems to work OK.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!