Ya, the car did have a vinyl top. The vinyl top on my was worn out and the bottom trim below the side windows were rusted really bad. I advise you to keep the vinyl top or get it redone professional (if in bad shape). I tried using the bottom plate and trim for the back window from a Caprice (didn't work), but the vinyl top's back window and side windows are set back compared to a regular hardtop. So the way I did it, would be consider the ghetto way, was used weatherstripping around the back window. Then I welded some metal around the back window and used body filler. The side windows, I ended up using body filler, but it will probably be ruined by water being trapped behind the original side window trim that mine had. Base on the pics of your Bonneville, your vinyl top looks to be in pretty decent shape. IMO, keep the vinyl top (landau top).