Actors rehearse for “I Do! I Do!” The show stars Chad Fornwalt, Esther Covington, Steve Lebens and Mary Beth Luckenbaugh. (photo by Lindsey E. Moore)

American Century Theater couldn’t have picked a better time to stage its new spin on “I Do! I Do!,” the 1966 musical about a man and woman’s marital tribulations. With the recent demise of the Defense of Marriage Act, it’s only appropriate that instead of one heterosexual couple, there will be three types of couples — straight, gay and lesbian — played by four actors.

But the timing of the U.S. Supreme Court decision was just a happy accident. “The choices for this were all artistic, not political,” insists director Jack Marshall, who also serves as ACT’s artistic director.

By adding actors and tweaking the script — removing references to slumber helmets, for example — Marshall hopes the Broadway production-turned-dinner theater standard can once again have universal appeal.

“Everything about the marriage is so rooted in the mid-20th century, but it doesn’t have to be,” the director says. “It’s as easy as showing some of these scenes with a same-sex couple.”

The idea came to Marshall while scouting a performance of the musical at the Lazy Susan Dinner Theatre to see whether the show might be a contender for the group’s season. The show was clearly dated, but Marshall was already imagining a modern alternative.

“Am I crazy or is there virtually nothing in this play that wouldn’t work just as well with a same-sex couple?” Marshall says he wondered. “It seemed to me that it would be extremely revealing and interesting and appropriate, especially now.”

The musical, adapted by writer Tom Jones and Harvey Schmidt from the play “The Fourposter,” is a series of vignettes that begin with the wedding of Michael and Agnes. It follows the pair on a well-known trajectory through childbirth and midlife crises, among other milestones. In ACT’s version, the couple is the more gender-neutral Leslie and Chris, and Marshall has set up three parallel universes so the audience can experience the same story in various ways. The acting switches might take place between scenes or in the middle of one.

Concepts are difficult, and I’m always leery of them because often they are just a way to dress up a play and make it look a little different,” Marshall says. “You see this a lot with Shakespeare — Let’s do ‘As You Like It’ about professional skateboarders — and it doesn’t really change anything. It’s just a lazy way to spruce it up and make people think it’s new.

“But in this case, it actually organically makes you see the play differently, even though virtually nothing in the show has to be cut or changed.”

Of course, the setup presents challenges for the cast. “It’s not jumping in and out of character so much as jumping into a scene,” says Steve Lebens, who plays Leslie. “Part of the scene has already been developed.”

For the sake of continuity, the actors have to take into account how their male or female counterparts played the role. Logistically, lighting should help camouflage entrances and exits.

“There’s one scene where three of us transition in and out of the bed, and it almost feels like you’re playing tag team,” says Esther Covington, who also plays Leslie (still following?). “Tap them on the shoulder and say, ‘Okay, roll over, you’re out now.’ ”

It almost sounds like a screwball comedy, and there are some sweetly frothy moments, such as a song-and-dance number called “I Love My Wife,” during which Covington serenades another actress, Mary Beth Luckenbaugh. But there’s also drama.

There are “these really tender moments between the two characters when they recognize their own fear of getting old and are able to turn to their spouse and find comfort in that moment,” Lebbens says. “As frightening as it is to get old for this character, I’m not doing it alone. I’ve got this partner in my life who’s always going to be there.”

In that way, the musical shows how it can endure. Our feelings about relationships haven’t changed much since the 1960s, even if the coupling looks different.

“It helps send the message that marriage is marriage and love is love. And that was the original message of ‘I Do! I Do!,’ ” Marshall says. “They just weren’t looking as broadly as the culture is looking now.”

I Do! I Do!

Through Aug. 17. Gunston Arts Center, Theater II, 2700 S. Lang St., Arlington. 703-998-4555. $35-$40; pay-what-you-can Wednesday.