"American Graffiti" is even sweeter the second time around. The freshness, lyricism and nostalgic humor that made the film enormously appealing in the summer of 1973 have enhanced by an additional nostalgic element - one's awareness of the subsequent careers of all the promising newcomers and relative unknowns in this phenomenal production.

Now in fifth anniversary revival at several area theaters, "American Graffiti" suggests a class reunion which turns out to be miraculously carefree, because virtually every old acquaintance you cared about has been prospering. It's an ironic joke on the movie's epilogue, one of the rare unsatisfying devices director George Lucas resorted to, in which the lives of the four principal boys in the story were updated, revealing that two of them had met untimely deaths. Nothing very bad seems to have happened to any of the key contributors to "Graffiti," beginning with the illustrious case of Lucas himself.

Lucas' second feature, "American Graffiti" was made when he was 28 and reluctantly bankrolled by Universal on a measly budget of $780,000. About 10 percent of that sum was spent to secure rights to the 41 rock 'n' roll songs, circa 1955-1962, that are used so evocatively as a musical accompaniment to and commentary on the episodic plot. The plot ingeniously compresses many of the good times, reckless pranks, frustrations and longings of a particular American teen-age generation into a single night of cruising in a small Northern California town.

Universal, along with every other studio, once before had rejected the script, devised by Lucas in collaboration with the young husband-and-wife screenwriting team of Willard Huyck and Gloria Katz. Universal relented only when Francis FOrd Coppola, fresh from the triumph of "The God-father" and eager to help his protege Lucas, agreed to produce it.

"Graffiti" stands in 13th place in Variety's list of all-time box-office hits, with rentals of $47,308,000, a figure destined to increase after the current revival. Lucas spent the four years after "Graffiti" preparing and shooting a little diversion call "Star Wars," which became No.1 on the Vartiety chart within a year, returning a reported $127 million in rentals to 20th Century-Fox from the United States and Canada alone.

The most conscious character in "Graffiti" was Curt Henderson, a witty, introspective teen-ager feeling pangs of homesickness on the eve of his departure for his first year of college in the East. The role was played by a somewhat pudgy but irresistibly smart, incisive, good-humored young actor named Richard Dreyfuss. It was the beginning of one of the brightest film acting careers of the decade, climaxed just a few weeks ago when Dreyfuss won the Academy Award for his performance in "The Goodbye Girl."

Lucas and Dreyfuss could quit tomorrow and remain legendary figures in contemporary film history. In fact, Lucas now insists, rather maddeningly, that he has "retired" or "dropped out" from directing. He seems to have no immediate plans to direct again, although he will supervise production on a sequel to "Graffiti," a sequel to "Star Wars" and a new comedy script, "Radioland Murders," by Huyck and Katz. Many people in the business expect him to evolve into a production chief par excellence, a cross between Irving Thalberg and Walt Disney.

If Lucas and Dreyfuss are the preeminent graduates of the class of "Graffiti," they aren't the only members of the class who've made a professional mark. Cindy Williams, cast as Curt's sister Laurie, became a TV star on "Laverne and Shirley." One may appreciate her talen even more under the direction of Lucas, whose restraint seems to enhance the ammation and emotionality that are allowed to go bananas on TV.

Ron Howard, who plays Steve, Laurie's boyfriend and Curt's best friend, was probably the most familiar member of the cast when the movie was first released, since he had been a fixture on Andy Griffith's television show for eight years. Since "Graffiti," he has become a fixture playing straight adolescent to Henry Winkler's Fonzie on "Happy Days," a series obviously inspired by "Graffiti" and responsible for spawning "Laverne and Shirley." Howard has also directed and starred in a couple of successful knockabout quickies for Roger Corman called "Grand Theft Auto" and "Eat My Dust."

Paul Le Mat, who played the gallant local folk hero, John, the undefeated drag racing champion, ought to become a star sooner or later. It might have beeen sooner if "Citizens Band" hadn't been retailed to poorly. Le Mat's performance as the frustrated, do-gooder hero of "Citizens Band" was one of the most appealing characterizations of last year.

Mackenzie Phillips, cast as Carol, the brash 12-year-old who tags along with John for the evening, now appears regularly as the eldest daughter on the TV series "One Day at a Time." HarrisonFord, the dragster who challenges John's supremacy, now stands on the verge of stardom after his performance as the impetuous, dashing Han Solo in "Star Wars." Lucas has restored three short scenes cut trom the initial release version. In one, Ford does an impersonation of Ezio Pinza singing "Some Enchanted Evening" in a futile attempt to amuse Cindy WIlliams.

Candy Clark, who won an Oscar nomination for her performance as Debbie, the drawling blond pick-up, has followed through with creditable work in "The Man Who Fell to Earth" and "Citizens Band." A high-school girl named Kathy Quinlan, who appears as Peg. Laurie's mischievous-looking best friend, in the scenes at the Freshman Hop, developed into Kathleen Quinlan - the doe-eyed young dramatic actress of "Lifeguard" and "I Never Promised You a Rose Garden."

The most amusing bit performer in the film is undoubtedly Suzanne Somers, whose current renown as a star of the series "Three's Company" gives her fleeting appearances in "Graffiti" a special kick. In case you'd forgotten, she played the mysterious, tantalizing blonde in the T-Bird who becomes Curt's great phantom passion after she mouths the words"I love you" out of her window and hangs a right turn into indelible erotic fantasy.

Although starring opportunities haven't come along for Charlie Martin Smith, whose performance as the wimpy Terry the Toad seemed even funnier than I'd remembered, his career has not languished. He's bound to be an invaluable comic character actor as the years go by.

Only the writers, Huyck and Katz, have suffered what might be considered a major setback: Their first credit "Lucky Lady." Now that they're reunited with Lucas, even that misadventure may be written off to experience.