Just to add another angle to this subject...
#302 came to me with its original short nut tacho cable, but later long nut replacement speedo cable. Both cables were in good condition, so the tacho one was simply cleaned and re-used. the speedo cable nut was shortened (still on the cable) and then re-used. Pictures below for comparison. Obviously the modified speedo cable does not have the slight taper, but good enough for me. To shorten the speedo cable nut, a small hose clip was fastened around it to provide an edge to cut surplus material from the nut lower edge, then moved little to provide an edge to file / polish away the "splines" to create a nut close in appearance to the tacho cable one. Fortunately there was enough surplus material on the nut to enable shorteneing and still be able to attach to the speedo drive. It was easier to do than I feared, just care an patience - oh, and I did prcatice on an old scrap cable first!
Cheers - Chris R