if a car is built up useing a new shell and all major componants are new eg engine it can be registered with the dvla on a prefix of that year i.e a new car. if the car was built from a new shell but numerous componants from a donor car were used such as the engine it would be registered on the prefix of the donor car. if the car was built using parts of an unknown origin then the car would be on a Q prefix. so this car was basicaly a fully new cosworth. also i know where there is a brand new 3dr shell for silly money! ford still had numerous RS500 shells up untill around 1995