I believe the 87' had a larger 5 bolt reed cage, and the later ones were smaller with a 6 bolt reed cage. Dunners like the 87' because of the high revving hp as opposed to the latter smaller reed cage motors that produced better torque. Some people on here say the 87' is just as common as any of the other years. Others have said otherwise. It may be a regional issue.  For instance michigan has a lot of members on here and they said there are a lot of them around up there. Around here in Missouri, I've only heard of a few in 15 years, and do see them for sale on Craigslist, but almost all of them are trashed.