I've found several threads in this forum and other sources about adding disc brakes to a 2000 and newer S series. They all pretty much say the same thing. Go to the junk yard and look for a pre 2000 Saturn with rear disc brakes for parts. And most say it's not worth it LOL.

 

I converted my 97 to rear discs and for me it was worth it based on the better brake feel alone.

 

I converted my '98 SW2 a few years ago, and it was well worth it. I'm now a convert.
From what I understand, cars that had abs, had rear discs.

 

The rear break parts are all the same, SL ,SC and SW. You will need the rear hub, obviously the brakes and the ebrake cable. The hub should have the "ears" to mount the caliper. If you have a autimatic you will have to change the ECU to one from gen 1 or 2. 3rd gen ECU is different for autos, but I am unclear why. I have a 2002 SL and plan to do the same job soon. It's a really straight forward swap the ebrake cable is the only hard part

 

You don't need to change the hub, unless it has a lot of miles, then a new hub with bearing may be a good thing. The ears for the caliper are on the knuckles. Yours may already have them, mine did.

 

95 and 97 SC2s here. Both w ABS. Both came w 4 wheel disc brakes.

 

I think around 98 or so Saturn discontinued the rear discs on ABS equiped cars.

 

I believe gen 3s except for the exception noted above.

 

I've seen several 99 SC2s with ABS and drums. Maybe discs were an option not standard for ABS at that point?

 

I have also seen exactly what you have stated.
Indeed, this sounds like the answer.