Look for the North American transplants to hike exports this year, as they add more destinations to the shipping roster, according to assemblers surveyed by our sister publication, Ward's Automotive Reports. Economists expect total U.S. exports to continue expanding due to improved U.S. competitiveness, a weak dollar and rising global economy, says the American international Automobile Dealers Assn. (AIADA). U.S. exports in dollar figures are forecast to grow from 7% to 12% over 1994 levels. Last year they increased by 1 0% to $512 billion, AIADA data indicates. Foreign-based automakers with North American assembly plants exported 184,932 passenger vehicles to countries overseas, reports the Assn. of International Automobile Manufacturers (AIAM). That's a 60% increase over the 115,378 vehicles shipped overseas in 1993. AIAM President Philip A. Hutchinson predicts overseas exports will surpass 200,000 units in 1995, which would represent at least an 8/. increase over 1994.