The antonyms for "after parts" depend on the context of the phrase. If "after parts" refers to the later portion of something, then the antonyms could be "before parts" or "front parts." However, if "after parts" refers to the posterior or rear end of something, then the antonyms could be "front parts," "head parts," or "foreparts." In a different context, if "after parts" refer to spare or replacement parts, the antonym would be "original parts" or "old parts." Therefore, it is important to understand the context of the phrase before determining its antonyms.