Bolts, especially Grade 8 are a bad idea for chain hooks, they're not rated for that type of load. Inspectors will ticket you and possibly red tag you until you replace the tie downs with "approved" gear. Grade 8 bolts will shatter if you side load them enough, Grade 5 will bend.
I always just used roll pins instead of cotters to retain the pin, left a couple with cotters for those times when you just have to remove the hook in the field.