I'm pretty sure the SIDO info is lost now. They had it back about '87 but since then... Like I said, a good look at the hanger brackets is a tell-tale.
Some historical detail:
Page 11 of the XA catalogue reprinted in the Ford Falcon Collection (A.C Bushby, 1987) lists the option of the 2V as "Special 250 CID, 170-horsepower Six..."
Footnote on the same page states: " (f) Dual exhaust available only with 302 CID and 351 CID V 8 engines"
Going back to the XY catalogue, page 23 gives this footnote: " (e) Dual exhaust available with 351CID V 8 only"
As I said, can't rule out "never on any car". There are some uncoded cars and custom builds, too (hearses and other variants mostly). Leather seat trim was another thing that very occasionally sneaked into some cars, I understand. Ah well, the mystery lives anther day.
Adam.