By Thomas R. CutlerCompanies designing products for customers to their own specifications are part of a unique worldwide club of engineer-to-order (ETO) firms numbering 200,000-plus. Even firms that have been exclusively engaged in repetitive manufacturing are now increasingly finding profitable client demand for customization. Almost 90 percent of these unique one-of-a-kind manufacturers have annual sales of under $50 million and have yet to unify the key parts of the process into an integrated business information system.