Detroit executives are understandably nervous about the billion-dollar investments foreign brands have made in Southern U.S. assembly plants. From full-size pickups and SUVs to minivans, the new vehicles coming from those plants are poised to attack Detroit's last stronghold, according to the Detroit Free Press. But the Japanese and the Germans are nervous, too, the Free Press said. Trucks are Detroit's best products, which is why careers are riding on vehicles like the segment-straddling Mercedes-Benz GST crossover wagon, which goes into production in Vance, Ala., late next year or in early 2005. That's just part of an expansion that also will double the number of M-class SUVs the plant can build to 160,000 a year. Nissan freely admits that it enters the full-size pickup wars with no credibility. Because of that, according to the Free Press,it's going to make sure the 305-horsepower Titan full-size pickup is such a bargain that buyers will be willing to overlook the fact that Nissan never built a big truck before. For years, GM, Ford and Chrysler have bragged about improved quality, greater efficiency and the hot new products they have coming. They've said their trucks are second to none in the world. We're about to find out whether consumers agree, according to the Free Press.