EVER ON the prowl for potential theatrics, the body snatchers seldom have been busier.

On various stages we've been having, or are about to have, such reincarnations as Walt Whitman and Winston Churchill, Helen Keller and Evita Peron, Christopher Columbus and Wolfgang Amadeus Mozart.

Nobody's safe. Eva Braun and Clara Petacci have just ended a London "Summit Conference." Eva and Clara? They were the mistresses of Hitler and Mussolini.

Even blood still coursing through the veins doesn't make one sacrosanct. Diana Ross and Federico Fellini are at the roots of two current musical smashes.

With misguided assurance that it's in the "Masterpiece Theater" class, NBC last week unleashed a vulgarity about the Vanderbilt clan. Its heroine, who hit it rich in the rag trade, her name sewn to countless bottoms worldwide, promptly canceled all public appearances for the next two weeks.

And Elizabeth Taylor has taken up the cudgels for both the quick and the dead by trying to halt an ABC teleplay about herself titled "The Elizabeth Taylor Story." Snorted Taylor: "I am my own commodity. I am my own industry."

Such materialist allusions are not only prime Taylorisms, but also God's truth. There's always been gold in grave-robbing. The Greeks gossiped about Oedipus long before Sophocles put him on a stage, and Saxo Grammaticus wrote about a real prince named Amleth nearly 4,000 years before Shakespeare turned his name's last letter into its first.

So, yes, making drama from the lives of real people is entirely understandable, though the trick is harder to pull off than it would appear. For all the known facts, the lifeblood of drama lies in imagination or imagery. The telling factor is in the texture, how the work feels, its richness of material, an artful seamlessness, an underlying pattern, the roughage of tweed, the softness of velvet, the smoothness of silk. An assured weaver creates a unique, defined texture.

Such a dramatist is William Gibson, whose "Monday After the Miracle" is so splendidly performed at the Eisenhower. Here, 23 years after he emblazoned our stages with "The Miracle Worker," Gibson continues the absorbing relationship between Helen Keller, the child of silent darkness, and Annie Sullivan, the teacher who happened on the word "water" to unlock a trapped mind.

With the playwright's instruments of imagination and imagery, Gibson portrays the two 20 years later, now both women in their physical prime. Into the home they share while Helen tackles calculus at Radcliffe stalks a 25-year-old male, a writer in search of Helen's own story.

Thus, a variation on the eternal triangle. John Macy, the interloper, is drawn to Annie, some 15 years older than he. Looking at him, she can realize what her devotion to Helen has cost her as a woman. Inevitably, as Gibson imagines it, Helen also is drawn to the young man.

The conflicts are sensitively imagined. The awkwardness of Macy's relationships with pupil and teacher are dramatically realized through skillful writing and staging. It is a tribute to actor William Converse Roberts that, in a basically unsympathetic role, he makes the conflict credible and holds his own with Jane Alexander's smoldering Annie and Karen Allen's awakening Helen.

Only when we dig up the facts do we recognize the playwright's dramatic contributions as well as his omissions. The facts are set forth in Joseph Lash's 800-page volume of 1980, "Helen and Teacher: The Story of Helen Keller and Anne Sullivan Macy."

Not surprisingly, the facts are far more complex than dramatization allows. Helen outraged many of her helpful contemporaries through her liberal political leanings. Like Eugene O'Neill, Annie Sullivan suffered the stigma of being Irish in 19th-century New England as well as scorn and neglect from those who ignored her role as Helen's key to knowledge. John's marriage, rooted at best to but half of his partner, would collapse through his alcoholism and his constant begging for funds.

The dramatist's challenge is to compress this plethora of material. What to leave out? What to include?

For example, Gibson's depiction of Pete Fagan, the man who wanted to marry Helen and ran away with her, is but a shadowy reflection of reality. Instead, Gibson has chosen to accent his three main characters, an understandable choice.

Inevitably, there is no scene to match that climactic one of "The Miracle Worker," the moment when Helen linked the signed word "water" with what trickled into her hand. While this makes for a play quite different from "The Miracle Worker," and while the final act lacks focus, Gibson's dramatic style is undeniable.

In his Christopher Columbus play, "Knight of the Ocean Sea," recently at the Hartke Theatre, Warren Adler faced choices that have defeated the more experienced before him: French dramatist Paul Claudel, Belgian Michel de Ghelderode and Meredith Willson, whose Broadway musical "1492" was short-lived.

Adler plods heavily in his exposition; with that out of the way, he unloosens for his second act, relying on his imagination rather than strictly on fact. But even though he moves in the right direction, Adler doesn't succeed in bringing life to the Columbus story, any more than any of the others.

By contrast, "Inherit the Wind," scheduled to be the second subscription play of the new Elizabeth Taylor-Zev Bufman production firm, is a work of absorbing texture. Here Jerome Lawrence and Robert E. Lee, recognizing the licenses they would have to take for the Dayton, Tenn., "Monkey Trial," chose other names for familiar ones: Matthew Harrison Brady, Henry Drummond and E.R. Hornbeck standing in for William Jennings Bryan, Clarence Darrow and H. L. Mencken. The freedom the author gained by the use of aliases allowed for sharper, more dramatic characterization.

Both "Amadeus" and "Inherit" are exceptional in recent plays-from-reality for their heavy production demands and scores of roles. "Amadeus" retained the real names of the characters, but in this case the course of history and the range of ideas provided the texture.

Literary types have become a prime source of the single performer format in the National Portrait Gallery's current "Portraits in Motion" series. Actor Will Stutts, an Alabama Yalie who was a founder of the Los Angeles Shakespeare Company, began this fall's parade with his "Walt Whitman: Liberal and Lusty as Nature," to be followed by Washington Irving, Herman Melville and William Faulkner. Here the author has a built-in insurance policy: His subjects provide the words, and their words are pretty terrific.

From Robert Manson Myers' award-winning "Children of Pride" comes another theatrical event for the Portrait Gallery: four dramas Myers culled from the letters of the Jones family of Georgia, dating from 1829 through the Civil War. Shepperd Strudwick is among the players who will be seen in the four dramatizations to be presented Nov. 19, 20 and 21. Since American TV mini-series seem devoted to utter schlock, it's time Britain's "Masterpiece Theater" had a look at this historical treasure trove. Myers' collection and meticulous editing are of "Masterpiece" standards.

Two of these four "Children of Pride" works are monologues, that style evolved early in his career by Hal Holbrook for his "Mark Twain Tonight." Holbrook, who keeps his performances fresh by varying his material each time, is tentatively scheduled to bring Twain to the Kennedy Center in the spring, and Eugenia Rawls will return to the National Portrait Gallery with her one-woman characterization of Fanny Kemble in June.

Winston Churchill, both a passive literary figure and an active military hero, inevitably now has his one-man show at Ford's, a theater that relies heavily on this genre. Devised by Sam Gallu, it is acted by Roy Dotrice -- last at Ford's at Herbert Mitgang's "Abraham Lincoln." There's also a Churchill musical under way, "Winnie," an idea from Sir Winston's granddaughter, Edwina Sandys, written by Robin Hardy and to be staged by Albert Marre.

In the case of the inexpensive one-man show, economics seem to motivate the body snatchers. But such is not always the case. Three current New York musicals cost in the millions: "Sophisticated Ladies," "Dreamgirls" and "Nine," inspired by Duke Ellington, Diana Ross and the Supremes and Federico Fellini. "Evita," about the Perons, continues its deathless cries for Argentina, and Dale Wasserman was adroit enough to combine Cervantes' life and fiction for "Man of La Mancha."

And while those dancers whose rehearsal confessions led to "A Chorus Line" are anonymous, we're assured that they've been getting royalty checks.

Grave-robbing is indeed a long established, profitable theatrical industry. All too often, one resents its distortions, inaccuracies, even downright falsehoods. But the playwright's imagination may have the odd effect of forcing our forgiveness of his sins.

Still, you do have to admire Elizabeth Taylor, our own, earthbound E.T., for her defensive clarity: "I am my own commodity. I am my own industry."