Why don't you replace the entire backstay, using stalok or norseman. While the wire may last longer, it must be old(ish) too, if the swage is cracking?
I have a 1977 Orion S&S 35. The fixed backstay's swaging is crackin. I was thinking of buying a long nut sta-lok and cutting the cable to fit. Or what about converting it to a running backstay? Would this benefit me or go against the design too much?