So true - that is why I love classic racing - different makes/models from different countries all have a good blast on the track.
Rules do change seen the T&C rules change - once alternate materials were permitted if originals were rare/NLA then changed to read only factory spec body work...now changed again to allow alternate materials via approval from the H&C Commission. If someone is taking a long time to build a car like me (and it was 1/2 complete went I got it and that took 8 years to get to that point and I have had it for 2 years now) if I was going to T&C under those 2009-2012 era then I might have installed fiber glass panels only to come out the other side and find they were illegal....no legal again if approved via the Commission.
Update: Thinking about how the rules change over time this is why the CoD exist - is it not?