In pursuit of an A-list ensemble on a $60 million budget, Warner Bros. spent months tinkering with the cast of “The Gangster Squad” — and with the addition of Emma Stone, it appears to have it.Move not only delivers director Ruben Fleischer (“Zombieland”) names on par with comparable period crime pics such as “L.A. Confidential” and “The Untouchables,” but it also shows that Warners is serious about staying in business with the fast-rising Stone. Thesp went into negotiations for “Gangster Squad” just as Warners prepares to open “Crazy Stupid Love” Friday, in which Stone stars opposite Ryan Gosling. “Gangster Squad” will reunite them, playing opposite Sean Penn, Josh Brolin, Anthony Mackie, Giovanni Ribisi and Michael Pena. Stone would play Jean, a sharp-tongued siren caught in a love triangle with Gosling’s character and Penn, who portrays mobster Mickey Cohen. Warners, which is co-producing with Village Roadshow, had no comment on Stone’s casting. Will Beal is penning the project based on the Los Angeles Times’ seven-part series “Tales From the Gangster Squad,” to which Warners acquired the rights two years ago. The articles, by Paul Lieberman, chronicled the LAPD’s efforts to keep East Coast mobsters out of Los Angeles in the 1940s by forming the Gangster Squad. Insiders tell Variety that Stone would segue from “Gangster Squad” to Mike Diliberti’s upcoming action-comedy “Little White Corvette,” though Stone’s reps declined to comment. Dan Lin and Kevin McCormick are producing “Gangster Squad” through Lin Pictures and Langley Park, respectively; Jon Silk, of Lin Pictures, is co-producing. Arriving at the current “Gangster Squad” cast wasn’t easy — before the pic was even greenlit, the studio and Penn went back and forth before the thesp came on with Gosling and Brolin. After that, names including Tom Hanks and Jaime Foxx showed interest, but eventually passed with insiders saying money became the obstacle. Stone has had a busy summer. In addition to “Crazy Stupid Love” Stone also stars this summer in Tate Taylor’s “The Help,” which DreamWorks opens Aug. 10. Thesp was also at Comic-Con last weekend to promote Sony’s “The Amazing Spider-Man,” which bows July 3, 2012. She is repped by WME and Anonymous Content.