No horns in the 623 and 624. The Trainmasters, Alcos, and GP7s have horns, although some model numbers may not. For details, check http://www.postwarlionel.com/diesel.html
Some postwar NW2’s had operating horns:
601 Seaboard (1956)
602 Seaboard (1957-58)
616 Santa Fe (1961-62)
617 Santa Fe (1963)
621 Jersey Central (1956-57)