If it didn't have it - it should. When I did this work on my 90 it was there and got replaced. It fits in a groove on the engine-side of the flywheel and IIRC looks more metal like than rubber. You need this part.

Oh, I'll second the suggestion about just replacing the disk. Once it's got oil on it it's toast. I'd also resurface the flywheel while it's out or at least clean it really, really well.

john