Somebody around here knows, but I'm sorry... It's not me.
I only ever researched going from a '92 to '77 and under.
When that proved to be more than I wanted to do, I just painted my existing grille.
I kind of looked into going the '85-'91 route, but I got hung up somewhere, and I can't remember what the issue was... or even if there was an issue.
I might have just changed my mind.
I just went to the LMC catalogue and saw pictures of the various grilles.
You can kind of see some of the attachment points on each style.
That might be of some help?
Here's a link to what I was looking at:Link to grilles