Cybill Shepherd Says Austin Butler Has Work Cut Out For Him as Elvis

Cybill Shepherd -- one of Elvis Presley's famous exes -- says Austin Butler will probably kill as the King, but it won't be a walk through Graceland based on what she remembers.

The famous actress, singer and model -- who was an "It" girl in the '70s, and who briefly dated Elvis during his Vegas days -- told a photog at LAX Saturday that Austin will likely be great as her old flame. She's seen a photo of him, and suggests he's a dead-ringer.

However, when it comes to portraying the life of Elvis on the big screen ... Cybill says it best here -- "I think it's a rough row to hoe." That means it ain't gonna be an easy role.

As to why, Cybill shares an interesting story that she played a role in -- and that she later learned the full alleged details about. She says she read a book that detailed Elvis' life and, allegedly, while the King had her in one room of his Sin City hotel ... he'd also have two other women on the same floor. Cybill makes a crack about that ... seems like she believes it.

Speaking of womanizers in Hollywood, Cybill sheds some light on some of the most famous men she turned down -- including Jack Nicholson, De Niro and Les Moonves -- and gives an interesting reason as to why she snubbed those dudes in their heyday.