FIA APPENDIX K
Federation Internationale de l'Automobiles (FIA) defined historic motorsport in art. 1.1 of Appendix K to International Sporting Code
1.1 The FIA has created the regulations in Appendix K so that Historic Cars may be used for Competitions under a set of rules that preserve the specifications of their period and prevent the modifications of performance and behaviour which could arise through the application of modern technology. Historic competition is not simply another formula in which to acquire trophies, it is a discipline apart, in which one of the essential ingredients is a devotion to the cars and to their history. Historic Motor Sport enables the active celebration of the History of the Motor Car.
FIA established Historic Rallies not as just another discipline to win trophies, but as a unique discipline of motorsport,
preserves period specifications and prevent application of modern technology;
expresses devotion to the history of motorsport;
celebrates of the History of the Motor Car.
In all other respects Historic rallies are just as the modern car rallies. The sporting and safety rules are the same. Competitors of modern and historic car competitors tally side by side in the same events, on the same roads and same special stages, share the same service parks and fueling zones.
If your historic car had no power brakes, no power steering, no ventilated discs this is how you compete. You cannot modify the car beyond what its FIA homologation says. Use any non period technology is strictly forbidden. You compete in your car as you would have competed in it in WRC events in the period of its homologation. This is the essence of historic rallies. That is the very fun, the challenge and unique satisfaction Historic rallies offer.