“Cars” is poised to pass the box office finish line in first place this weekend, but will it race away with a record? Tracking puts the toon on course to come close to and potentially beat the two biggest Pixar bows: “The Incredibles” and “Finding Nemo,” both of which grossed $70 million. The film opens at 3,985 theaters. That puts “The Omen,” which is at 2,723 playdates, on pace to be a solid No. 2 this weekend with a likely gross in the 20s. However, horror pics often fall fast at the box office, and it remains to be seen what impact the unusual gambit of drawing auds to theaters on a Tuesday will have on the weekend. In the only other release this frame, Picturehouse is hoping “A Prairie Home Companion” will prove effective counterprogramming as it bows at 760 locations.