Federal regulators should hold off on approving a hookup between the Nasdaq Stock Market and OptiMark Technologies Inc.'s electronic trading system, a group of trade-clearing firms said. A committee of clearing firms at the Securities Industry Assn., Wall Street's trade group, asked the Securities and Exchange Commission to first resolve concerns about the anonymity of the OptiMark system. . . . Bank of America Corp. said Monday it's combining money management units catering to wealthy people, institutions and mutual fund investors into one group "to more effectively serve client needs and build our business."