I have a set of osborne assembly manuals but hard to see what kind of screws and the finish !
The simple reason is that there are no dimensional descriptions on hardware included in the Mustang Assembly Manuals. This is a common practice in engineering and assembly line procedures. It's all coded.
The lines going from the screw in question will go to a letter ,the letter corresponds with the same letter in a list somewhere on the page in the manual . The letter on the list will indicate a number which identifies the fastener. You look that number up in another book that you need called the "AMK guide to fasteners ". You will take the number associated with the fastener in question that you found in the assembly manuals and find it in a list of numbers in the back of the AMK book . When you find the same number in the back of the book it will give a page to turn to . On the page you will find a picture of the screw . Also when you look up the specific number on the page it will give the size and the length of the screw. The finish is also given when you find the number initially on the assembly manual page . There is a glossary in the AMK book that translate the letter and number into the finish . The assembly manuals are great for the illustrations the numbers for fasteners you have to use the AMK reference to translate. The AMK book is typically sold by the same vendors that sell the manuals.
There is a short cut you might try. In the Library Section of this forum under the title of "Mustang Hardware Spreadsheets, 67-68" you will find two spreadsheet attachments, one by application, MHW67-68AP01, and one by part number, MHW67-68PN01. You can find the description of the part in question in the latter spreadsheet. The spreadsheets are based on the "Mustang Assembly Manuals" and "AMK Guide to Ford Fasteners". There is another list of finishes in the Library - "Finish Codes - Short List". Try them.
Jim