According to The Best Plays of 1965-1966, on August 17, 1965, director Will Holt replaced Don Francks, and female understudy Lee Beery (aka Leigh Beery) replaced Trude Adams.
Before the closing, Kenneth Nelson and Christina Bartel (aka Christine Bartel / Joan Bartels / Joan Kobin) joined the cast. Clearly, Nelson took over Francks's assignment, and we think that Bartel took over Adams's assignment, but the Showcard program we've seen with inserts for Nelson and Bartel does not make much clear. (It does not help that the program listed only the titles of the songs performed but not who performed what.) The original cast is still listed in the actual program. Beery is listed as one of the two understudies. (Gene Lindsey is the other understudy.) Women's Wear Daily reported that Bartel joined the cast just for closing week. We have not found any press mention of Nelson joining the cast.