Speedometer cable weirdness

Update: Installed the Y804, and it works. And the needle is nice and smooth now. $10 on Amazon. It is a few inches too long in the engine bay, but I tied it to the brake line so it doesn't interfere with the transmission shifter linkages. Thanks guys. Oh interesting, the part that screws onto the transmission, is round. The original cable that I removed attached via a large hex nut.