If needed, rethread with a die tool.
Yes, everyone has a set of right and
left handed dies hanging around.
Seriously, the only sensible way to shorten a stay is to cut it and fit a field terminated, compression-type fitting, like a Hi-mod, Norseman, or Sta-lok. I've done this on the shrouds and backstay on my Catalina 36, to add toggles to the shrouds and a backstay adjuster to the back.
Determine the thread size, left or right hand, and select the part for wire size. The wire side is usually the right hand thread. Cut the stay by taping with electrical tape and sawing with a hacksaw. It's remarkably easy to cut.
Rigging Only is the best source I know. I've purchased from them, super service, and fast.
Have you checked the rest of the rigging to verify the PO didn't swap a couple of them? Before I started cutting, I might get the tape out and verify the lengths of all the rigging against the manual.
This is an excellent suggestion. The backstay is usually longer than the forestay, maybe they were swapped.