My Citroen appears to be a 1984 CX GTi 2500

While it a VIN number, this seems to belong to a 1976 car.

In Citroen Service Manuals, I see diagrams suggesting the sub-frames, the DIRAVI assembly, and the 'body-shell' have additional identifying numbers. (It is not clear if these are duplicates of the VIN originally stamped on the front fender/wing, or some other number.

Can anyone tell me where exactly to look for an identifying number on the rack-&-pinion, or either the front or rear sub-frame?