This is one of those mid-year running changes that is poorly documented as it involves three different engineering groups that got into finger pointing - "It goes on an engine, let them document it." vs "It's an electrical requirement, let them document it." vs "It's the transmission guys responsibility." That being said, the stud was first used in early or mid 66 (maybe on late 65, I don't know) production on cars with an automatic transmission to allow the transmission cooling lines to be attached to the RH front of the block prior to the battery ground wire being attached. Previously, on AT cars, the bracket and ground cable were attached the same as the manual transmission cars, a bolt (lockwasher omitted for clarity) as shown in the Assembly manuals. This can be seen in the illustrated section of Ford Car Parts, Sect A71, pg 6 as part number 380818-S.
I believe that p/n 380818-S is for the I-6 engines, as it should have a 3/8-16 thread at the block end, and a 7/16-14 thread at the battery ground end. The AT bracket goes in first with lockwashers, the battery ground last, with lockwashers and a jam nut. This type of installation make is easier to replace the ground cable. The part number for the 289 V-8 engine is unknown, but it has 7/16-14 threads at both ends. It should be used on any 289 engine with an AT including HP and Shelby applications.
I don't know if this applies to years other than 66 and 67, or other engines (302, 390 etc).
Jim