Don't waste your time with the dealer. You'll find that standard bolt at home depot or autozone. Looks like the previous owner improvised and used a different bolt. This would surely mess up the entire thread in the block. Expect to put a helicoil or similar for a more permanent fix. I did this repair on my bottom alternator bolt. I used a china made helicoil kit M-10 X 1.25 for less-$20-ebay. And used the oem size bolt. Seems to be holding up for about 6 months now. Good luck.