I often find the cars with all dates matching very close to each other are a lot of times put together after gathering parts for years. These cars did not come with all the dates as close to each other as many want to believe. Its easy to build a car this way if you were to take years and gather parts all very close in dates. But this was not what was built originally.
Depends on what components you are talking about. Also, what model and what year. Some things, like engine components assembled by the engine plants, are often very close together.