The only Cougar that we know came factory equipped with this part is the Cobra Jet. According to the Master Parts Catalog (MPC), any Cougar with a 3.91 or 4.11 rear end and a C-6 would have been equipped with this reducer.
This is a part that we will probably never have on hand, but would love to document. If you have one of these adapters, we would be interested in being able to put detailed pictures of it on this listing. Please let us know. We hope to have a reproduction of this adapter available shortly.
Ford Part #: C8ZZ-17294-A.