That picture isn't mine, it's from the online catalogue. Thought it might herlp because it shows the orientation and at least one fitment point for the brackets.
Do you think the brackets might be supposed to fit on the captive nuts rather than the studs? Might be worth a try.
Try emailing Hitchcocks directly, they are usually very helpful.
The answer may be that it appears no two Indian Bullets are exactly the same so bracketry tends to be a "We'll do our best but you might have to do a bit of fiddling when it arrives" kind of affair. Which is certainly borne-out by the three I've had over the years. I've taken parts off one which fitted perfectly and found they wouldn't fit the other one without some serious whacking with a rubber mallet.