The novel's description of some of the characters is completely different from their screen portrayers. To be true to the novel Clemenza (Richard Castellano) and Luca Brasi (Lenny Montana) would have to change places (ie. in the novel Clemenza was tall, while Brasi was shorter and heavier). Also, in the novel Fredo was much more of an imposing guy; he was described as being much tougher.