I have a 48 chev coupe that has been updated and is a wonderful cruising vehicle except for excessive wind noise from the rear, seems to be around the rear of the roof. Is this normal for this model?? could I be missing insulation in the headliner? The rear window is tightly sealed, but it does appear to be plexiglas(lot of scratches).

Any help or ideas would be greatly apreciated..

Thanks in advance

Jerry