I think that nylon spacer is only for Pre 1986 cars with diffrent shocks and springs. I've got them on my xr4i (1984).
And i can tell you're not missing anything!

The part E is just 2 separate parts before 1986 (E and B separate). And after 1986 It is just one part (E and B as metal one part). Pre 1986 and after 1986 are both the same height.