Lynn, that's the 250-mile Daytona American Challenge Cup race. There were many different racing series that ran (and still run) at Daytona, not just NASCAR. The #4 car next to the 1963 Tempest was Mickey Thompson's car, driven by Bill Krause. It had one of the "Mystery Engine" 427's under the hood.
It was a banner day for Pontiac, and an embarrassment not only for Chevrolet, but Ferrari and Ford as well. To have a sedan take out the most elite 2-seat sports cars in the world was something that shook up the racing world. That's why Mercedes-Benz bought the #50 Tempest and shipped it back to Germany, to disassemble it to see what made it tick.
Pontiacs dominated NASCAR in 1962 winning 22 of 53 races. The other races were split between Chevrolet, Plymouth, and Ford.