A Westport real estate firm is seeking to create a new, mixed-use building and adjoining row of townhouses at the northwest corner of Forest Street and Locust Avenue—site of the long-vacant former Bank of America building. In an application filed on behalf of Silver Heights Development, officials said they want to put a mixed-use building with 1,500 square feet of ground floor retail uses and two residential units above facing Locust Avenue, and five townhouses fronting Forest Street. Schematics included in the Aug. 24 application show that the mixed-use building would run to the corner of Forest and Locust. The application for the .4-acre lot at 42 Forest St.—from attorney Jacqueline Kaufman, a partner at Stamford-based Carmody, Torrance, Sandak & Hennessey LLP—includes two proposed changes to the New Canaan Zoning Regulations in order to make the project possible as it now is envisioned.