General Motors Corp. on July 15 announced it would manufacture a new mid-sized pickup called the GMC Canyon. According to GM, production of the 2004 model-year pickup will start in late 2003 at GM's Shreveport, La., plant, which also will produce the 2004 Chevrolet Colorado pickup. The Canyon, scheduled to arrive in GMC showrooms in early 2004, will be sold in the United States and Canada. It will share GM's GMT355 mid-sized truck platform with the Colorado. The Canyon will replace the GMC Sonoma pickup, which will end production at the Linden, N.J., assembly plant in late 2004. GM did not release details on pricing, production or product features.