Chrysler Motors Corp. on Tuesday named Thomas Stallkamp chairman and Forest Farmer president of its Acustar Inc. parts subsidiary. Stallkamp assumes the title previously held by Bob Lutz, chairman of Acustar and of Chrysler Motors, the automaking arm of Chrysler Corp. Lutz remains chairman of Chrysler Motors and a member of the corporation's board. Stallkamp joined Chrysler Motors in 1980 as a general purchasing agent and moved to Acustar last June as vice president for marketing and procurement. Farmer succeeds Lee H. Runk, who resigned Monday to become president of the St. Louis-based Harvard Industries, an auto parts supplier. Farmer has been with Chrysler for 20 years and has held a number of managerial positions. He most recently was general plants manager for car and truck assembly operations. Acustar, created last year as Chrysler spun off its parts operations, employs about 28,000 hourly and salaried personnel and runs 30 factories nationwide.