From pickups to tractors, Fleet Owner's preview of 2004 commercial trucks highlights how the slow economy, new emissions regulations and competitive pressures are reshaping the vehicles fleets buy. As a result, some manufacturers eliminated certain models, while others made no changes to their product lines. Many truck makers, however, are offering redesigned products, with some introducing new models not seen before in the U.S. Every effort has been made to ensure that all of the 2004-model information presented is as comprehensive and accurate as possible. And if in some cases 2004-model plans were not available at presstime, we've tried to offer at least a glimpse of what might be coming from those manufacturers as the year progresses.