"When It Dries" was cut at some point during the run, and "Poppa Knows Best" was considerably shortened.
Different performance totals are given in different sources. The Best Plays of 1970-1971 lists a run of 351 performances, but Variety and Theatre World both reported 343. While most of the time we would be inclined to trust Variety and Theatre World over Best Plays, in this case Best Plays seems to be correct.
Some online sources report 6 previews, but that is incorrect. There were 14 previews, starting on October 28, 1970. There was originally to be only one Broadway preview, but the show opened was overlong at the time of the first tryout performance in New Haven. One contemporary stated that the first performance in New Haven ran four hours, but other reports placed it around three hours of performance time plus an intermission, and that seems to be correct. Much cutting and reworking was deemed necessary, especially after poor reviews greeted the Boston opening that followed New Haven.
By the end of the run, three of the eight cast members had left the show: Walter Willison, Madeline Kahn, and Harry Goz. All three left near the end of the run and were replaced by their understudies. Willison was replaced by John Stewart (not the original understudy for Willison's role of Japheth), Kahn by Carol Tenney, and Goz by Jack Davison.
There is some uncertainly as to the dates on which Willison and Kahn left. The Best Plays of 1971-1972 listed August 16, 1971, as the date on which Stewart and Tenney replaced Willison and Kahn. On August 23, 1971, however, the Daily News reported that Stewart would be taking over that night. On Thursday, September 2, 1971, the Daily News mentioned in a theatre column that Tenney had just joined the cast, replacing Kahn for the last two weeks of the run. This seems to suggest that Tenney had taken over on Monday, August 30, 1971.
Best Plays listed September 6, 1971, as the date on which Davison replaced Goz. In this case, we have found nothing to suggest otherwise.