Well, the actual GLASS parts are interchangable. There is a metal mounting system that holds the glass/reflector on that is different from 85/86 to 87+ as the grilles are mounted in slightly different methods. I have had to swap from one mounting system to the other and its not hard. There are I belive 2 or 4 bolts on the back of the housing, just unbolt from the donor car and bolt the good glass/reflector to your old housing.
Or you may get lucky and find one from a similar year. Come by here and I will even help you install it (I'm in Beaverton)