Montana Power Co., Butte, is considering investment changes as a result of a recently completed asset allocation study for its $283 million defined benefit plan, said Treasurer Ellen Senechal, who declined to say what specific changes are being considered. A decision is expected by October. Separately, Brandywine Asset Management was hired to replace Firstar Investment Research & Management as a $28 million small-cap value U.S. equity manager for performance reasons, Ms. Senechal said. Marian Zentmeyer, CIO for Firstar, did not return phone calls by press time. Mercer assisted.