Ralf,
If you looked in the Library section of this forum, you will find a topic "Mustang Hardware Spreadsheets, 67-68". There are two files you can download, one sorted by part number (MHW67-68PN02.XLS - the "02" is the revision), the second sorted by application (MHW67-68AP02.XLS). In the application file under "Molding,Fr,Wheelwell(opt)" (Molding is the preferred spelling for Moulding) you will find the part number (381671-S45X) and description of the screws you need. You can then find them by part number in many Mustang parts store, I recommend AMK. I realize the shipping cost and minimum buy requirements tend to be rough for shipping to Germany, but there is the information you need.
Jim