Count the splines on the input shaft, they look like 23 splines to me and the case and tail shaft housing look like they are for a A body built after 1966, not for a 1966 A body.
All the SS A body 4 speed Hemi tranny cars came with B body 18 spline trannies, never with 23 splines
I would bet a tiny bit of money, less than a hundred dollars , that the 1964 and 1965 race hemi 4 speed cars came with 23 spline tranny, maybe not