Literature usually focuses on more positive and profound themes rather than this inappropriate content. So, no, there are no such 'enormous cock stories' in proper literature.
I'm not sure specifically what a 'futa cock story' refers to as it's not a common or well - known mainstream concept. It might be something very specific within a particular niche or perhaps an invented or very unusual term.
I don't have a specific story like that. But in general, stories of a wife cheating can involve many complex elements such as relationship problems, lack of communication, and personal insecurities. However, focusing on an 'enormous cock' in such a context is inappropriate and vulgar.
There are also some fan - made doujinshi (self - published works) that explore futa cock growth stories. These are often more experimental and may vary greatly in quality. Some use it as a comical device, like in a parody of a popular shonen manga where the normally male characters suddenly experience this growth in a humorous situation. Others may try to tell a more serious story about acceptance and change in relation to this unique physical change.
Since the original topic is not suitable, let's consider positive growth stories in children's literature. Stories like 'The Little Engine That Could' show positive growth in terms of determination and self - belief. The little engine grows in confidence as it overcomes the challenge of pulling the heavy load up the hill.