Mr. Roxy,
That's because A HOLE IN THE HEAD was about a 'player' who was about to lose custody of his eight-year old son to his more stable brother and sister-in-law.
GOLDEN RAINBOW was about a 'player' who was about to lose custody of his eight-year old son to his deceased wife's sister--a workaholic pain in the butt who needed therapy and knew as much about child raising as Cinderella's Stepmother.
The musical's authors didn't modify the source material, they twisted it into a pretzel. Arthur Schulman, who wrote original play the film was based on and whose idea it was to musicalize it, walked off his own production.
Steve Lawrence hated backstage politics on show so much (particularly how his wife Gorme was treated) that he vowed he would never do another Broadway show again. And he hasn't.
"I say YOU'RE the CUTEST one. No, I say YOU'RE the CUTEST One. And we go on like that from dawn to three."