The "bathtub" idea was developed into an operational concept car in 1946, called the Cadillac Interceptor. It was never shown to the public. GM really were thinking that it was the future, but, as you say Silvercloud, Mr Earl decided otherwise. Some elements of the shape did transition into later designs. I wrote about it in the April 2018 edition of Retroautos (Here is the link: https://www.shannons.com.au/club/news/retroautos/retroautos-april-fords-luxury-landau-a-vauxhall-collection-cadillacs-secret1946/). GM were able to find for me some images that had never been published, along with images of what became of the car. From the research I've done, it was clear that Ed Glowacke was Earl's intended successor, but he died from cancer at an early age.