I just recently went through this here in CA. Back in 2006 when my 96 had about 50k miles I replaced the OEM cats with Catco cats mainly just to save the OEM's for a later date. In 2006 the CA laws were not as strict so I was able to order the non CA compliant Catco cats from Summit Racing.
Fast forward to now the Catco's were totally garbage with the catalysts inside falling apart and rattling inside the cases. I was surprised they were junk after only 50k miles of use, but as others have said they are poorly made. Btw, the Catco's look nothing like the OEM cats, so don't assume the smog techs won't notice the difference. Luckily I still had the OEM cats, so I threw them on with 4 new Denso 02's, new Autolite iridium plugs and Summit Racing plug wires. My 96 which now has 102k miles passed with readings that were similar to when it was new.
If I would have needed new cats the best option to save $ would be to buy some universal "weld in" CA approved Magnaflows. Just cut out the bad cats and weld in the new ones. Now you'll have new CA approved cats with the correct CARB stamp on them plus they'll be in the stock location using the factory tubing.
Steve