'90 Chevy Sub. exhaust question

Well, the tailpipe rusted off right behind muffler so I had to wire up the muffler and take off the tailpipe. My ? is should I replace the whole system including the cat or just replace the tailpipe after the muffler. I have 109000 miles on this vehicle and am leaning to replacing the cat and then just straight piping it the rest of the way. Any thoughts?

If the cat. is working , keep it and replace the rest.