Superbird Race Fenders Explained
Chrysler supplied special front fenders for the race Superbirds as shown here.  These pieces do not have the front inner reinforcement like the street car has.  On the street car, the hood pins attach to this assembly. 
As you can see here, there is no place on this fender for the hood pins.    A Coronet inner panel must be added to use this on a street car.     You will sometimes see these fenders floating around at swap meets. 
Here is a photo of the Ramo Stott #7 Superbird from inside the left front wheelwell.    You can see there is no inner brace at the front.    Also of note is that the sidemarker opening is riveted over.  The lower valance panel is riveted to the fender, as is the nose cone.   This is typical of the way the stock cars were put together.
From the top side, you can see the unique racing upper radiator support where the hood pins attach.  The center portion of the radiator support is removeable to make engine changes easier.