differences between FIA and USRRC comp cars?

[ALF]

Hello

Which where the differences between FIA and USRRC comp cars?

As I'm driving my car at some national & international Hill-climbing races, I would really appreciate to have it looking like the original cars. I know it will be impossible to be 100% accurate, as it is NOT an original, but I can tray to be very close to it! And at the end it will be still my car, whit my personal look, but I would like to the right changes on it! In addition I'm in a lucky position, as there are coming a lot of winters, here in Switzerland, and therefore it could be done in smaller steps.
1.) Race seat
2.) Weber carburettor and some changes under the hood
3.) Fuel splash shield
4.) .....

To do this I would really appreciate, if you could help me with some picture and information. As my car has a street-style dashboard and no FIA trunk, it would make sense to step into the USRRC direction.

Many thanks for your help and wish you all the best for 2007!
ALF