BEVERLY HILLS, Calif. — It was a clash of the titans when Robert Aldrich cast Joan Crawford and Bette Davis in the gothic film, “Whatever Happened to Baby Jane?” in 1962.

The two actresses had been the reigning queens of Hollywood for years — Crawford the penultimate “star” and Davis the consummate “actress.”

Now for the first time they were working together in what was, at best, an armed truce. Some years later Aldrich reported that they had been perfectly well behaved on the set. “They spend the rest of the time saying what a cow the other one is,” he said.

Young audiences will have the chance to see what a cow the other one was when FX premieres its limited series, “Feud: Bette and Joan” on Sunday starring Jessica Lange as Crawford and Susan Sarandon as Davis.

Ryan Murphy (“American Horror Story”), executive producer of the series, says he didn’t want to emphasize the kitsch prompted by casting these two legends in such a film at the end of their careers. “I wasn’t really interested in doing anything that was, quote-unquote, campy or a campfest,” he says.

“I was interested in something a little deeper and a little bit more emotional and painful. I think ultimately what happed to both women is very painful. I got to know Bette Davis. I had a very minor relationship with her and got to spend time with her, and the thing about her is you go into something like that expecting a very larger-than-life camp figure, which she helped, I think, propagate. And she told me when I talked to her, that she felt that she was never going to be anybody unless somebody could impersonate her.

“So in the public view, she rarely turned that off. She felt that was important for her survival. But when I got across from her one-on-one and I got to one day spend four hours talking with her, she was NOT that person at all. She was not camp. She was not broad. She was very emotional and real, and all of those things were in the water when we began to write the show.”

Lange pored over information on Crawford. “The thing with Joan is she was never NOT on, and some actors, by nature, are just not that way. When she was in public, she was performing. So it was very hard to find a moment where you could really discern what the heart and soul of (her) character was. So then as an actor, you go back to, ‘OK, well, this is what happened to her in her childhood. This is what determined who she was — the physical abuse, sexual abuse, the poverty.’ All these things, she was constantly fighting against for the rest of her life. She had a fifth-grade education. As she says, ‘Everything I learned, I was taught by MGM: How to walk, how to speak, how to present your face. I mean, EVERYTHING.’ So there is this great artifice.”

What interested Lange was depicting Crawford without this synthetic front. “Then you actually can invent what you would imagine was inside her. And there are a few little hints that I got. Like, if you listen to Crawford, she spoke the way a lot of actors — especially coming out of the silent films like she did — were taught to speak by the studios and by the dialect coaches that were brought in from New York, this very kind of upper class, mid-Atlantic accent. And a couple times I heard this San Antonio thing come through. Whether she was drunk while giving an interview, or caught off guard in a moment. But that was the other great thing, because Joan was alcoholic. So there are moments where everything falls away, and there is this kind of ugliness and brutality to her, that I think she is a fascinating character to play.”

Sarandon was terrified to play Davis, but Murphy eased her into it, assuring her that she was up to the task. “And that really helped me a lot,” she says. “And I said, ‘Well, I have to have a dialect coach, because her speech pattern is the antithesis of mine.’ I’m so sloppy and slow, and she has got that thing that’s been imitated so many times. And there is a great guy named Tim Monich, who I’ve worked with before, and so they very generously got him. So he was there making recordings of every scene that are still on my telephone that I could listen to at night when I got home, or on the way, and in between, and then on the set, until he got snatched up in another production …

“And Ryan also does a very good Bette Davis. Sometimes he would correct me, and say, ‘But you have to hit that harder.’. . And so I think it was an exercise in surrender and trust, and just jumping in and hoping for the best and channeling Bette in some way, but hoping that she’s pleased.”