I have a 97 Eclise RS. I did the conversion from Rear Drums to Rear Discs. Basically, you will need rotors, calipers, hubs, and brake lines. Goto http://www.2gnt.com.
Look at the modification section. There is a write up on how to do the conversion. (Just MAKE SURE you use a 10mm Flare Wrench for the brake lines.) http://www.allmitsubishi.com
sells the conversion kit for $250. Of course these parts aren't new, they are junk yard parts. I noticed an incredible difference. The car stops much better and the brake doesn't feel spongy. Besides, the discs look MUCH better than the drums. (Painting the calipers didn't hurt)