Thanks, I was wondering about the fit of the bolt and spindle, and you answered that too. Proper torque and fasteners (nylock nut or locking nut) should prevent most issues. I think I'll be going this route too, sounds like a great fit.
You are right, the stock pin does step down for the threads, they're M12. My main concern was the fit of the 5/8 bolt... mostly about oblonging the hole if the bolt is too loose in the hole. Your answer was really what I was looking even if my question sucked, much appreciated