Some years ago a friend of mine bought a Mk4 XR3i. A few months down the line he was tugged by the police and informed it might be stolen, so they impounded it to try and identify it. There was no chassis number in the floor as the front floor section had been replaced. The police couldnt confirm the I.D of it so my mate got it back. It was referred to the DVLA who placed it on an age related plate and it was assigned a new chassis number. Dont know how it works now though.