Working on my throttle linkage, I found the "stop nut", or whatever it is called is damaged.   Most of you will recognize this as the carburetor end of the linkage.  This is on a 74 C model.   I have tried Aircraft Spruce and my local engine re-builder, but have not come up with either a name for the "stop nut", or a replacement.  Obviously, the one I have is useable, but it's "broke", so I'd like to have a new one.   Anyone?