Towers Financial, a New York leveraged buyout firm, said it will propose to the five unions of Pan American World Airways that a partnership be established to buy the airline from its parent company. Under its 12-point buyout proposal, Towers would set up a new management team and board of directors. It also would try to purchase half of Trans World Airlines' computerized reservations system and resume its association with the American Airlines reservations system. Towers said it would seek to re-establish Pan Am's Pacific routes, which were sold to United Airlines last year. There would be substantial union membership on the Pan Am board, but labor groups would be asked for a no-strike clause and other concessions.