ALLEGHENY INT'L <AG>, FIRST BOSTON SET MERGER Allegheny International Inc said it has entered into an agreement to merge with an affiliate of First Boston Inc's <FPC> First Boston Corp in a transaction valued at about 500 mln dlrs. Allegheny said the agreement calls for holders of its common to receive 24.60 dlrs a share. Holders of the company's 2.19 dlrs cumulative preference shares will receive 20 dlrs a share and those owning its 11.25 dlrs convertible preferred will receive 87.50 dlrs a share. Allegheny International said the agreement calls for the First Boston affiliate to start a cash tender offer for all outstanding shares of Allegheny's common, cumulative preferred and convertible preferred. The company said First Boston has committed to provide all financing necessary to acquire such securities in the tender offer which is estimated to be about 500 mln dlrs. It said the agreement is also subject to the waiver by March 13 of certain conditions under the company's existing bank credit agreement. Allegheny International's statement did not name or describe the First Boston affiliate involved in the agreement. It did say the offer for the company's stock will be conditioned also on the valid tender of securities representing at least a majority of the voting power for the election of directors of the company and the valid tender of at least two third's of the outstanding cumulative preferred and convertible preferred shares.