The stage musical opened in 1968 and starred Tom Bosley as H*y*m*a*n K*a*p*l*a*n (so spelled because that's how he would write his name). It had a book and score by Rosten, Paul Brand and Oscar Brand. And the supported cast, while unknown at the time, was notable, including Hal Linden (later a Tony-winner for Harnick and Bock's The Rothschilds and TV's Barney Miller) and Donna McKechnie, who later starred in A Chorus Line among many others. The show actually had a lot of connections to Harnick and Bock, and in particular their Fiorello! Tom Bosley, of course, starred in that, and another of the supporting cast in The Education of..." , Nathaniel Frey played Bosley's assistant lawyer in Fiorello! And the show was directed by the legendary George Abbot...who, yes, had directed Fiorello!
Alas, the show did not have anywhere near the same success. (And in fairness, it wasn't written by Harnick and Bock, nor its book writer Jerome Weidman.) And it only lasted 29 performances. But apparently there were a lot of things to admire in the show -- 20 years later, in 1989, despite its earlier lack of success there was a revival of sorts in New York, and it had a limited run, and this passage was part of the New York Times review -- "One can have a very nice time at this musical, although it is not the strongest evening of theater in sight. It is amusing but not uproarious, and its score is sprinkled with some clever tunes.…The work is funny and bright for much of the way, and it is ingratiating, even with its failings." Hardly a rave, but not remotely what you expect to read about a big flop.
For what it's worth, Tom Bosley came through it all okay. Six years after the show closed, he got hired to star as the father, Howard Cunningham, on Happy Days.
As I said, I haven't yet found any footage of the show -- whether Broadway, or any community theater production -- but I did at least come across one song from the show. So, that's a start. It's called "When Will I Learn!," performed by Nick Palmer. The song isn't a showstopper, and is a bit overproduced, but there's a charm to it and builds nicely, so I can see it fitting into the show nicely, most especially if done is a smaller, quieter way.