not really a u-joint.
ball and trunion.

older cv type joint.

they always seemed to die on me. the spherical bearings didn't hold up well over time, and no one at the time I had one made new one's. you were lucky to find nos stuff in a few places to repair or replace it.

that is why the go to trans was the 65 so you got the regular slip yoke and u-joint setup everyone else ran, but still keep your push buttons.