No it is the large, long bolt that passes through the frame plates at the bottom of the down tube. My Bullet is a 2006 and it does have metric hardware on it but I don't honestly know these machines as well as you and some of the other members here and I do think there is mix on this bike. If push comes to shove I'll just replace the entire bolt. The other alternative is go through my dreaded "Hell Bucket", A five gallon pail of nuts and bolts that I've tossed in there for 20 odd years. Dumping that on the floor and pawing through it is the equivalent of root canal work for me and my last choice.
My '08 also has a combination of all three (or 4?) thread specs so it makes it interesting to say the least.
This doesn't help you, I know, but I'm lucky enough to have a really well-stocked Ace Hrdwr. 10 minutes from my house. They have a huge selection of not only nuts, bolts and screws, but a whole McMaster-Carr catalog of tray after tray of goodies to look through.
There are also mockups of male & female threads & pitch gauges, etc., that you can match your part to. There is also tray after tray of EVery kind of washer imaginable EXCEPT the copper crush for my main oil drain plug. Go figure