That setup carries a 1964 Ford part number (C4OZ-6B068-E), was still offered in the 1966 Shelby American parts catalog as a Cobra branded accessory. Doesn't appear in the 1968 Cobra Kits catalog, although I personally saw one of those manifolds 40 years ago that said SHELBY rather than the normal COBRA. Only one I've ever seen. Hope this helps.
Dave
Dave