For info

I was able to get a new after-market cat for about 60$USD.  Depending on
your situation and what you'll do with the van, it may or may not be
worth just doing it "right" the first time.

Also I'd strongly suggset changing the O2 sensor while you've got
everything apart. My install went a lot smoother with a new O2 sensor +
cat b/c the old sensor.

Best regards
Shawn