I thought I broke the shift cable but it turns out one of them came unattached at the transmission. How are these supposed to stay attached? Should there be a c-clamp or something holding them on? It feels like they had rubber stoppers of some kind on the screw but they have deteriorated. I was thinking I could unbolt the mounts and drill a hole in the center for a pin if there wasn't another way.

Thanks for any help.

They pretty much "clip" on. Check out rodneydickman.com for some rebuild kits for them. Good stuff, oiled brass with all the hardware.