As far as I can tell after looking at a lot of Distillates, is that they started extending the upper horn sometime around the mid-80s. All the early 80s Distillates have the shorter upper horn, while all the mid and late 80s distillates have this more extended upper horn. But note, they all have the same small lower horn, which makes the overall body shape different than the Spoiler style body, which has a more extended lower horn as well.
Curt