some 1200 speedos have are slightly different, so not all speedo cables are the same. found this out when i put my coupe dash in the the speedo went up but wouldnt come down again
was good if i wanted to know the fastest id gone, but not much use for anything else. had the grind down the little brass bit at the back of the speedo and slightly shorten the bit of the cable that went into the actual speedo

also with stumpy boxes the speedo cble comes very close to the exhaust so a decent amount of body clips or something are needed to make sure you dont melt the cable