After nearly 65 years of producing a staple of the American theater, the Good & Plenty Manufacturing Co. is being sold.

But the nation's moviegoers, the biggest consumers of the licorice confection, shouldn't worry. Good & Plenty's current owner, Warner-Lambert, plans to make and store enough of the tiny pink and white candies to keep everyone supplied during the months it take the new owner, the Switzer Candy Co., to move the candy plant from Philadelphia to St. Louis.

According to Warner-Lambert, Good & Plenty, which also makes Rothchild candies, "did not fit into the long-range plans of the company." Warner-Lambert is a pharmaceutical company and also manufactures such products as Dentene and Trident chewing gums, Listerine, the Parke-Davis line of pharmeceutical products and Entenmann's baked goods.

Warner-Lambert said it will close the Good & Plenty plant in northern Philadelphia and lay off its 140 workers in late September or early October.

Kenneth Eakes, president of Switzer, a division of Beatrice Foods Co., said all equipment from the Philadelphia factory will be moved to St. Louis and production will resume in February or March of next year.

Switzer Candy Co. has been making licorice products for 100 years. The addition of Good & Plenty and Rothchild will double the company's business, Eakes said.