I might be inclined to believe that there were some unusual cars that left the factory or were changed at the dealership. Looking at the build sheet for my 58 Belvedere, there is a field labeled 'Equipment Changes' as well as one labeled 'Special Equipment'. In the field labeled 'Special Order' at the top of the sheet, someone has hand written '558'. Trying to figure what that meant. I guess anything is possible. Ron |