NationsBanc Montgomery Securities Chief Executive Thomas Weisel is apparently weighing whether to leave the firm he founded almost 30 years ago because of escalating hostilities with NationsBank Corp., which acquired his firm for $1.2 billion last year, sources said. According to the sources, who spoke on condition of anonymity, tension between Montgomery's founder and the bankers at NationsBank have been rising for months, particularly over issues such as whether the San Francisco-based investment banking firm could keep its name, among other concerns. But the last straw, sources said, was a dispute over control of Montgomery's lucrative junk bond business. Although NationsBank had said it would let the Montgomery junk bond team run the business of underwriting and trading junk bonds, it recently decided to place Edward Brown, NationsBank's head of capital markets, in control and move the business to Charlotte, N.C., where NationsBank is based, the sources said. Weisel, 57, reportedly threatened to leave two weeks ago, said the sources, who predicted that he would leave this week or immediately after Montgomery's growth stock conference next week, which is expected to draw 2,000 investors and representatives from 200 companies next week. A spokeswoman for Montgomery could not be reached for comment. A spokesman for BankAmerica Corp. in San Francisco, whose merger with NationsBank is nearly complete, also could not be reached for comment.