The multiracial-cast revival of “A Streetcar Named Desire” has taken further steps toward Broadway, booking Nicole Ari Parker and Blair Underwood to star in a production targeting a spring 2012 opening.Parker (“Soul Food,” “The Deep End”) will topline as Blanche DuBois in the 1947 Tennessee Williams play alongside Underwood as Stanley Kowalski. Emily Mann (“Anna in the Tropics”), a.d. of Princeton’s McCarter Theater, helms the show. Producer Stephen Byrd has been pulling together a diverse-cast staging of “Streetcar” for a few years now. In 2008, he produced an all-black production of Williams’ “Cat on a Hot Tin Roof” that yielded a healthy profit on Broadway prior to a run on the West End. Byrd had already held the Broadway rights to “Streetcar” prior to the Off Broadway arrival of a much-praised production of the play toplined by Cate Blanchett. That incarnation was buzzed about for a potential Main Stem run, but the transfer never materialized. Theater, opening dates and further casting have not yet been announced for the latest revival. Most recent version of “Streetcar” to hit the Rialto was the 2005 Roundabout staging that starred Natasha Richardson and John C. Reilly.