they usually have track cars and festival cars for other big time people to drive around in during and before the race...
Seems that 50 or so "festival cars" usually get made. Most of the time they are fairly identical to the real pace car(s), minus the lights, etc. For example, in 1995 and 1998 the festival cars were standard indy replicas. In 2004, the festival cars had the indy badging, but the paint was all blue (looked like a standard CE car, plus a few decals).
The festival cars are not necessarily the same car as the pace car... in 1990, i believe the pace car was a convertible beretta?, but the festival cars were corvettes. An educated guess says that this years festival cars were convertible corvettes, as the Z06 is pulling so much money right now...
Also, there are also usually 5 or so track cars made, in case something happens to the main one... these are hard to come by, and really expensive (read, outside my price range

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