It appears that there are differences between the early 86.5 to 88 and the later 89 to 92 distributors. Here are some reference photos.
86.5 to 88
http://japan-parts.eu/toyota/us/1987...tributor#19100
89 to 92
http://japan-parts.eu/toyota/us/1989...tributor#19100
I'm not sure if there are any differences in the head they were meant to go into.