Well I finally got my $200.00 wagon running. The previous owner cut the cats out of the exhaust as he thought the car was dead. Looking for some economical replacement cats. I see some single cat systems available. Since they have bungs for both O2 sensors, do I really need a second cat?

No, it will run fine without the rear cat, might throw a cel though. My 99 has a broken off sensor going to the rear cat and it doesn't have any cell and runs fine. Someone might have put an o2 eliminator on it before I got it though.

I have a 99 outback and from what I was told 98 and 99 are the exact same part numbers vs 97 or 00. Mine didn't come with a rear cat o2 sensor. So I think just a single will work