Robert Weede's alternate in the original cast of Most Happy Fella was Richard Torigi. He performed on both Wednesday and Saturday matinees.
I don't recall ever hearing that Robert Ryan or Geraldine Fitzgerald ever had alternates as the Tyrones in the 1971 revival of Long Day's Journey Into Night.
I'm not sure if a Saturday matinee was scheduled and on Sunday there was only one performance.
The original production played six performances a week (Monday-Saturday evenings, no matinees) and began at 7:30---at a time when just about
every play started at 8:30 or 8:40.