New Style Hard Button Conversion
FYI for y'all. I just completed a new style hardbutton EATC (the bubble button style) upgrade using a '92 SHO EATC as the guts. This upgrade required NO Electrical soldering. Here is how I did it:
Essentially, what you are going to do is swap just the face plates of the old (1992) and new ('96 and newer) units while retaining the circuit boards and lighting from the old unit. The LEDs are almost the same size, so the old unit's board fits into the new unit's faceplate.
1. Find new style EATC that has the proper color buttons on it. (I'll call this the new unit for the explanation.) (I have a '92, so I wanted the blue-green display, not the green-green display)
2. Find the proper EATC for your Gen 2 SHO or if you are brave use your existing one. (I'll call this the old unit this explanation.) I actually found a bone-yard '92 unit even though I was looking for a '93 or newer unit. I was going to do the resolder the faceplate thing, but couldn't find the proper donor unit for the electronic brains.
3. Disassemble the faceplate with buttons from the old unit - it will slip off from the faceplate circuit board revealing the LED display and switches. Also remove the main circuit board from the case. Do not break the ribbon cable that holds the faceplate circuit board to the main circuit board. Do not remove the LED display from the old unit's face plate circuit board.
4. All of the large buttons (ex. "Automatic", "Outside Temperature" and "Off" on the old unit use a single switch in the center of the back of the button, while all of the new units use a double switch with a switch at each end of back of the button. This is why everyone says that you just can't switch the faceplates. Disassemble the faceplate from the new unit. On the back of the new unit's faceplate near the plastic display window will be two plastic alignment nibs for it circuit board. These nibs need to be removed so that the faceplate will make contact with the old unit's circuit board.
5. Remove the rubber button contact sheet from behind the buttons of the new unit. Find some strong, yet light and thin clear plastic and create a "bridge" between the ends of the buttons. (I used some clear plastic from an old broken EATC that held the smaller buttons in place.) You want clear plastic to let light shine through it to illuminate the buttons. Super-glue the bridge to the back of the buttons on the new unit. Just use a drop of super glue - too much will glue the buttons permantly in place and then you can throw the whole project into the trash. Make sure to test the buttons for movement after they dry. Also, super glue some of the bridge plastic to the small "Blue" and "Red" temperature buttons above the "Outside Temperature" button so that you will have even contact between all of the buttons.
6. Once the bridges are dry, mate the faceplate to the case of the old unit's case. You will find that the old unit's case is a tad wider than the new unit's faceplate and that the alignment studs in the new unit's faceplate will not go into the slot on the old unit's case. Just expand the width of the slot towards the center of the case with a drill until the new unit's face plate will easily fit onto the old unit's case. When fully reassembled, the faceplate will not fit tightly onto the case, so you don't have to worry about the snaps mating properly.
7. Reassemble the old unit's circuit boards back into its case.
8. Swap the new unit's faceplate onto the old unit's face plate circuit board. Remember to retain all of the old unit's circuit boards and display. Position the old unit's button circuit board onto the new unit's faceplate in such a manner that you feel a tactile click with each button.
9. Place the new unit's faceplate onto the old unit's case using the alignment studs. I put small screws into the studs from the back to keep the faceplate onto the EATC case. Leave a bit of a gap between the faceplate and the case so that the buttons will have room to move. If you put too much pressure onto the back of the faceplate, the buttons will always be "on" and the unit will not work properly.
10. Install into your car. I relocated mine to where the stereo head-unit used to be. (I also have the '95 DIN storage bin instead of the flimsy double cup holder tray.) Unlike most people, I placed the EATC behind the stereo double-din trim plate because it looks neater than having the mounting portion of the faceplate exposed and that way you don't have to trim the ends of the faceplace; however, you have to really push to get the EATC into the dash because it is wider than a standard DIN, but once in, there is plenty of depth to handle the EATC. I also duct taped the EATC directly to the trim plate then reinstalled the trim plate. More work, but looks better.

One thing to note is that the '92 EATC has a larger number display than the new style, so when installed into the new style faceplate, the very top of the display is a little harder to read when the EATC is installed in the head unit DIN slot. (For example the top line of the number 9 is harder to see, so it makes it look more like a 4.)
Hope this helps some one.
- Gil
'92 Green/Black (w/new style hard button EATC, '93 Console, and few other upgrades...)