In the New York Times on October 15, 1964, it was reported that Barbara Harris, Jane Connell and Lauri Peters would be in the production. Of the three, only Peters ended up in the production, playing Moll. Harris had played Moll in the Blitzstein memorial concert six months earlier. It's possible that Harris was going to play a different role in this production, but it seems more likely that Harris would have again played Moll, with Peters perhaps playing Sister Mister.
It would seem likely that Connell was expected to play Mrs. Mister, which ended up being played by Nancy Andrews. (Connell and Andrews had both played Mrs. Peachum at different points during the long run of Blitzstein's adaptation of The Threepenny Opera at the Theatre de Lys.)
In the Village Voice on Oct. 22, 1964, it was also reported that Harris was to be in the production. There was no mention there of Connell or Peters.