I think it goes like this:
1979: The return of the portholes and nose grabs.
1991: The return of the two-piece horns (I think this is what you meant!), side vents and screened roof vents.
1998: The return of the nose vents.
1999: The elimination of the bottom ridges.<<<
Let's not forget that PW sized coupler opening and coupler shields that reappeared sometime in the mid 90's.
Joe