Growing up in Maine, Patrick Dempsey always dreamed of driving in the Indianapolis 500. Now the Grey's Anatomy star is getting his chance — sort of. He's taking the wheel of the pace car at the "greatest spectacle in racing" this Sunday. As the pace-car driver — Lance Armstrong did the honors last year — he leads the 33 racers to the starting line at the Indianapolis Motor Speedway (aka the Brickyard). The 41-year-old actor is no stranger to motor sports. He's a co-owner of Vision Racing, an IndyCar Series team, and when his schedule allows he competes in off-road races. TV Guide: How did you land this gig? Patrick Dempsey: I've been to the Indy 500 three times. The invitation came through [Indianapolis Motor Speedwayread more