How do you shop – is you search by JLM2209, make sure you read the description. Usually it says up to or from VIN abcxyz.
It will also give the width in the part description.
Better yet – Google CENTRIC 11108260. This is for the solid rotors and it will set you back under $20.
If your car has the vented outboard brakes, then Google BECK/ARNLEY 0813197. Costs just over $20.
Steve
PS From what I can tell, XK8 and 1996 XJS rear brakes are the same. So, no worries here regarding JLM2209.