FOR aficionados of off-stage drama, it doesn’t get much better than the story of “Legends!” – the ill-fated 1986 comedy by James Kirkwood that paired Mary Martin and Carol Channing as two faded and feuding movie stars.

A hugely hyped production back then, “Legends!” turned out to be a wild roller coaster of a ride, with tales of real-life battles breaking out among the stars, the producers, the playwright and the director.

Slammed by the critics on the road, “Legends!” never made it to Broadway.

Kirkwood, who died of AIDS in 1989, chronicled its odyssey in “Diary of a Mad Playwright,” one of the funniest and most insightful books ever written about the commercial theater.

Almost 20 years later, there’s a new chapter to add to the tale: “Legends!” is finally coming to Broadway, and this time its stars will be Joan Collins and Linda Evans, reunited for the first time since their “Dynasty” days.

Broadway producer Ben Sprecher told The Post yesterday that the new production will try out in Toronto in 2006 before opening on Broadway.

Collins will play Sylvia Glenn, the sharp-tongued (and sharp-clawed) movie star modeled on Joan Crawford, while Evans will play Leatrice Monsee, the seemingly sweet, gentle star, based on Loretta Young, who turns out to be an iron butterfly.

Why revive a play that was such a disaster the first time around?

Because, says Sprecher, the script is actually quite good.

“I was looking for a play for Joan,” he says, “something she would feel comfortable in. I read the script and thought it was very, very funny. I was prepared for her to think it was too lightweight, but she really enjoyed it.”

Sprecher also points out that, despite the bad reviews and backstage feuds, “Legends!” was a hit on the road.

According to news reports at the time, the production grossed $10 million during its 23-city tour, with a 20 percent return on the initial investment.

The reason “Legends!” didn’t come to New York, Sprecher says, is that Martin pulled out at the last minute, furious that the director cut her big second-act speech in which she talks about her battle with breast cancer.

“Mary went away and then Jimmy Kirkwood got sick, and the play fell between the cracks,” Sprecher says.

Kirkwood’s diary backs him up on this point.

When she learned the scene had been cut, Martin slammed down her script and said: “This is a very rare moment in my professional career. Not only is the speech ruined for me, but also the play is ruined for me. I will go on, but I will not play London, and I will not come to New York. I’ll fulfill my contract, and then you can get someone else and cut anything you want.”

Channing was equally blunt (and more honest about the script): “Oh, for God’s sake, if you’re going to please the critics, cut the whole damned play. Really!”

This scene is just one of many delicious moments recounted in “Diary of a Mad Playwright” (now, sadly, out of print).

There was also the night that Martin’s electronic ear mike, which she wore because she couldn’t remember her lines, started picking up taxi cab dispatches instead of cues.

It’s probably too much to ask that anything that bizarre will happen on this new production of “Legends!”

But we can always hope – and keep our ear to the ground.

SPEAKING of offstage dramas, the fir ing of Dallas Roberts from “The Glass Menagerie” gets curiouser and curiouser.

The latest detail to emerge is that Roberts exhibited very strange behavior during last weekend’s tech rehearsals.

Production sources say he began experimenting with his character in a way that shocked and offended the show’s star, Jessica Lange.

She practically had him fired on the spot, I’m told.

“Glass Menagerie” begins performances tonight with Roberts’ understudy playing Tom.

Christian Slater takes over starting next week.

CHRISTINA Applegate Watch, II: The critic for the Minneapolis Star Tribune caught the final performance of “Sweet Charity” and revised his opinion of our struggling little TV star.

Applegate, the critic wrote, “went deeper into her character and as a result was much more credible.”

My dinner bet with producer Barry Weissler – that he’ll have to replace her before the show gets to New York – still stands.

Yesterday, his press agent said he likes the Park Avenue Café.