In my 12+ years in San Diego, my guess would be no way to pass without a clean running cat.
I still have all my smog check receipts somewhere and the standards kept getting more and more stringent with every check. They hold you to the standards "they" set, not the standards that were in effect when these cars were new.
Trust me the standards are way cleaner now than they were even 10 years ago, let alone 20.