I know I'm replying to a really old message here, but maybe it will be of interest to other people in the future. I own a 1997 Toyota Supra twin-turbo, and I just installed a Rio Car MP3 unit in it. It was a major pain, and I'm still not real pleased with my installation. I had to cut the dash trim piece to make it fit, first of all. (When you remove the trim piece, you'll see that they have these plastic tabs on the back of it. Apparently, they help guide the trim piece so it slides around the factory double-DIN stereo easily.) They get in the way of the metal "cage" that holds the Rio pull-out stereo though - so they have to be cut off. I used a Dremmel tool w/cutting wheel to accomplish this. Then, I had to shave a couple millimeters of plastic off of both sides of the double-DIN opening on the trim panel, because the Rio stereo wouldn't slide in and out of the opening otherwise. (The Rio MP3 has screws on both sides of it that stick out just a little bit -- and the Supra's dash opening doesn't have enough clearance for the heads of these small screws to fit through.)
After all that, I *still* had problems, because the Rio wouldn't quite slide all the way into the metal cage. It wouldn't always make a good connection, so you'd only get sound out of the left speakers and weird things like that. I ended up cutting away still more plastic from the trim panel, so the stereo's faceplate wouldn't press up against the edges of the trim and prevent it from sliding all the way in.
Oh, by the way - just getting that metal "cage" mounted in there was a bit of a trick. The Supra's double-DIN opening is designed to come out as one piece, and let you screw your stereo into it. Since the Rio cage doesn't mount using screws, but instead uses those tabs you bend backwards - I had to find a couple tabs that would actually latch onto something in the Supra's mounting cage. I ended up using 2 side tabs on the Rio's cage (1 one each side) and bending them out and all the way backwards, so they were bent into a U-shape. That kept the Rio's cage from sliding out with the stereo when the stereo is pulled out. I had to mount the Rio on the bottom part of the double-DIN opening to make this work. It had nothing to latch onto at all if I tried using the top opening.
It all works now, but if I ever remove this stereo to sell the car or whatever, I need to buy a new trim piece first!