Gene Hackman is one of the cinema's most talented actors. This - after an Academy Award for his performance as Popeye Doyle in 1971's "The French Connection," and nominations for his work in "Mississippi Burning" and "I Never Sang For My Father" - is a given.

Some things you probably don't know about the man who rivals James Brown for the title The Hardest Working Man in Show Business:- He paints for three hours every day.

- He wishes he would have been born two decades earlier, so he could have made a movie with Rita Hayworth, that most tantalizing of movie redheads.

- He is fastidious. Meticulous. Squeaky clean.

He may be one of the few human beings alive who ever dressed for a heart attack.

The heart-scare business, which happened in early September, relates directly to his acting abilities. He is right up there with Dustin Hoffman and Robert Redford and Robert De Niro in terms of versatility, and, resultingly, is offered countless scripts. Unlike his peers, however, the workaholic Hackman has trouble disappointing people. Just say no? The phrase, up until recently, wasn't in his vocabulary.

Last year, for instance, Hackman, 60, did four films - count 'em,

four - back to back: the suspense thriller "Narrow Margin," the just-released "Postcards From the Edge," in which he plays a tough-love director disgusted with the drug habit of his actress, played by Meryl Streep; "Class Action," another action thriller; and "Dinosaurs," a political (what else?) thriller co-starring Mikhail Baryshnikov. That film done, he flew off to a little Oregon seaport to relax.

The respite from a grueling work schedule, says Hackman solemnly, musing on his health and films before a packed press conference in a Vegas hotel, just may have saved his life.

"I hadn't felt well for a day or two," says Hackman, who in person radiates the same fatherly warmth and low-key charm that he does on screen. "I knew something was going to happen."

And happen it did. Dull chest pains gave way to pounding aortal distress. "So I started to drive into Portland," he continues with an embarrassed grin, "but I didn't want to get caught out on the road. So I went back to my hotel, took a shower and put on clean underwear - all those things your mother tells you about, you know, in case you do end up in an accident."

Good grooming wasn't enough. Hackman also threw on a suit, then drove himself to the nearest hospital. "I didn't want to get into the emergency room and find myself getting ignored," he laughs.

The doctor's verdict: angina. "The doc said he'd like to go in and expand one of my valves, so he did that. It's a little sobering when that happens to you. You have to change your lifestyle. . . . He said I've got to stop all this stressful activity. That doesn't mean I'm not going to do any more action films. But I am going to take seven or eight months off."

While "Narrow Margin" probably won't be Hackman's last punch-and-pound potboiler, there's a better-than-average chance that it is the last movie to spotlight his personal heroics. Hackman fans, take heed: If you want to see Gene Gene the Stunt Machine dangle precariously from a swiftly moving train, only inches away from death, this may your last chance.

Based loosely on the classic 1952 RKO B movie "The Narrow Margin," this "Narrow Margin," scripted and directed by Peter Hyams, pits Hackman and Anne Archer against a slew of bad guys with underworld connections. Archer plays Carol Hunnicut, an ordinary woman who witnesses a brutal mob hit. Hackman is Los Angeles Deputy District Attorney Robert Caulfield, who rescues her from her assailants and then whisks her onboard a luxury train - the only mode of escape available.

But soon after the final "All Aboard!" the couple realizes that mob hit men also have purchased tickets and are hot on their trail. Suspense, action and some nifty stunts - with Hackman tethered to the slippery roof of the barreling locomotive - quickly ensue.

Caulfield is a typical Hackman achievement. In another actor's hand, the underwritten role easily could have become a cardboard action-adventure hero, all knuckles and little nuance. Hackman turns him into a multidimensional character. His hallmark is making the ordinary man seem extraordinary.

"He's instinctual about what will make his characters real," says director Hyams. "With this film, for instance, he wanted to make the character wear these little tiny spectacles. I said no. He said, `Let me try them on, if you don't like them, we'll go from there.' Of course he was right. The glasses made the character seem even more vulnerable, more accessible. Gene gives lots of little touches like that to a character."

Hackman, for his part, blushes and stammers when it is suggested that he's something special. "I think I look 21," he jokes, "and then I look up there on the screen and see a guy old enough to be my grandfather. I see the hair going, the weak chins, and the walk and I think, `He's silly."'

He pauses, searching for the right self-deprecating words. "I'm always a little disappointed with myself," he says. "I don't understand what I'm doing in the business. I don't see it. The talent. But if they hire me, somebody must be seeing something I obviously don't."

Hackman's career has not unfolded as he thought it would. As a child, his heroes were song and dance men - and the occasional rogue in tights - and he originally became an actor to get a shot at the parts his matinee idols conquered with equal parts brio and style.

"Errol Flynn, James Cagney, I loved these guys as a kid," he says. "I still do. As a young kid, I'd come out of the theater, walk by the lobby mirror and be shocked. I couldn't understand why I didn't look like Errol Flynn. I was so into those roles . . . "

By the dawn of the 1960s, when Hackman first started making films, the swashbuckling hero-types were out of vogue. He made his motion picture debut in 1964's "Lilith," but it wasn't until 1967's "Bonnie And Clyde" that he captured any attention (namely, an Oscar nomination for Best Supporting Actor).

"I had such a good experience on `Bonnie and Clyde' that I was spoiled," he recalls. "I thought all the films would be made up of a band of jolly-good players with great rapport. It was a rude awakening."

(Hackman notes that pal Warren Beatty - Clyde - asked him to participate in "Dick Tracy," but he begged off because of overwork.)

After a string of successes in the early '70s - "The French Connection," "I Never Sang for My Father" - Hackman fell on what he calls hard times. The dramatic roles he yearned for dried up, or went to others. After reprising his role as Lex Luthor in "Superman II," Hackman dropped out of sight for a couple of years, devoting his time to his painting and various theater endeavors.

Bored stiff, he finally returned to the film fold, this time in a succession of films in which he portrayed weary but wise action heroes. He liked the easy money those films provided, not to mention the high visibility.

Now, because of his heartaches, Hackman is moving into the third phase of his career. He'd like to do more parts like the ones he played in "Another Woman" and "Postcards From the Edge" - roles that test his talent.