I have an old-style 21-tooth, translucent-white in color (at the bottom of the pic).
I do not know much about the 65-older speedo gears though, regarding AT vs 833, and if 64 and 65 are the same (but I presume so, as 64 was the 1st year for the 833 and 1966 went to the bigger speedo gear). I do know it's hard to find, and the reproductions are long gone (in March I talked to the guy that made them), so be prepared that I do want some $$ for it.