Hemi Dart and Barracuda info needed

Guy’s , I need some info on these cars, specifically approximate build dates? I just received in an A body 4 speed for a friend to rebuild , and I’m thinking it could possibly be out of a factory Hemi A body. I’m posting a pic of the tab on the side of case which shows a build date of February 26 1968. Obviously it’s an 18 spline input shaft, but not sure how I could verify it to be a real A body Hemi box? I took the side cover off, and it has no’s springs or keys in the sync’s, it’s been slick shifted, or “crash boxed” . We’re these sent out this way from Hurst? Also has a solid mount for the Transmission mount, never seen anything like it. It’s boxed and welded, looks like it was professionally done not a scabbed up piece. Anyway I would like any help with identifying if it’s real, or not. I have been rebuilding these Transmissions for a long time and this is the first time seeing a Hemi A body box.

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