Paul Newman. Steve McQueen. Tom Cruise. Marsha Mason? "I love cars," Mason confessed to Parade magazine. "I've been racing about a year-and-a-half and I want to race competitively." When she was growing up in St. Louis, Mason said, "I'd go down to the pit and just watch the guys--I enjoyed the company, besides the normal pubescent kind of attraction." Maybe ex-hubby Neil Simon can write in a role for Mason in some sort of Grand Prix comedy. . . .