I haven't seen any such option.. Getting some mileage on my Peugeot now
Edit; Throwing in a question aswell.. Are there any great disadvantage with heavy mileage on the race cars, or would an engine and chassi restoration bring it back to factory standard?
Nope. Higher mileage just makes them cheaper. Engine restores give you more HP, and chassis restorations don't do anything. Waste of money in GT5.