If you are assembling something that specifies grade 8, you cannot use grade 9 as it is not a real SAE standard. Grade 9 is a proprietary standard and does not necessarily have to meet or exceed the standards of grade 8. It may, but it does not have to.

Pat, you should cut that bolt where it necks down and check for defects. Also, you need to find out who made the bolt and go after them. Very few bolts are made in the USA anymore, most are out of Taiwan. It's kind of hard for the SAE to regulate on them when they're half-way around the world.