Hi Tony, Welcome to the group.
The full DSO (Domestic Special Order) number is 6-digits. In the above example for car #0139, it is indeed "84-2512" (or 84x2512).
On paperwork, a full DSO number always includes a prefix of the Ford Ordering District. In the following clip from the microfilm file, the "DSO No." is "84x2612."
The "84" Ordering District prefix in the example above is actually comprised of two different pieces. "8" is the Region and "4" is the District (according to the breakdown on various Ford 80-column computer punch cards). When these two digits are combined, they are commonly referred to as the "ordering district."
This same Region+District code would also be found the first two digits a Ford dealer code. The 6-character dealer code is comprised of the region+district+zone+number, as evidenced by the following examples:
Vehicle Order Card
Dealer Delivery Card
Using the shortened version, the range for 1967 Shelby GT DSOs was 2501-2614.
The Ford vehicle punch card refers to the 4-digit number as the "Special Order Number," and it occupies columns 32-35 of the Vehicle record.
You may also find this page beneficial to understanding how to decode the 80-column record for a '67 Ford vehicle: