Re: XB Chassis numbers
The build sheet was by the factory ,put under the pasengerchair,and under the carpet/insulation.
If nobody has removed it ,You will be able to retrieve it from there.
It is a lightblue light cardboard a4 size document that traveled with the car all the way down the assembly line and was signed of before car release.
I have found both in my cars so far in the same spot.