Chuck, read the box, there are for 1992. However, the Viper was actually a pace car for the 1991 race. In 1992 they used a Cadillac Allante.
"The first prototype was tested in December 1989. It first debuted in 1991 with three pre-production models as the pace car for the Indianapolis 500 when Dodge was forced to substitute it in place of the Stealth, and went on sale in January 1992 as the soft roofed RT/10 Roadster."
1991 Dodge Viper Carroll Shelby
1992 Cadillac Allante Bobby Unser
1993 Chevrolet Camaro Z28 Jim Perkins
1994 Ford Mustang Cobra Parnelli Jones
1995 Chevrolet Corvette Jim Perkins
1996 Dodge Viper Robert Lutz
1997 Oldsmobile Aurora Johnny Rutherford
1998 Chevrolet Corvette Parnelli Jones[1]
1999 Chevrolet Monte Carlo Jay Leno
2000 Oldsmobile Aurora Anthony Edwards
2001 Oldsmobile Bravada Elaine Irwin Mellencamp
2002 Chevrolet Corvette Jim Caviezel
2003 Chevrolet SSR Herb Fishel
2004 Chevrolet Corvette Morgan Freeman
2005 Chevrolet Corvette General Colin Powell
2006 Chevrolet Corvette Z06 Lance Armstrong
2007 Chevrolet Corvette Z06 to be announced