Something to add from betterthanyou's post
General Swap Information:
"Serpentine belt front covers will not work on vee belt engines. In 1986 The S-10 used a combination vee belt and serpentine belt drive. This truck still uses the normal vee belt front cover."
That is MOSTLY true. There is some speculation that the lower part of the cover is the same on some early (two bolt design) 86 trucks as the 82-85, but the 86 cover's bottom design should fit like the 87. The ONE difference between that and the 87+ cover is the swirls in the cover. My guess is that there may have been left over 85 covers and pans, so they used them till they ran out on 86. That's of course an educated guess at best.
When I pull my engine and swap over the timing cover, I'll snap a pic and post it for sh*ts and giggles.