I started out by taking some measurements of the area around the stock head unit.
Two of my requirements for this project were that the screen should look as close to factory as possible and that it would not require relocation of the climate controls. From a few of the Firebird install threads I knew that a 7inch screen would fit just barely. My initial thought was to try to fit the computer itself behind the screen in the area occupied by the head unit. This thought led me to ITX motherboards and small cases. The Travla C138 case seemed to be of a reasonable size, but ended up not actually fitting in height or depth.
For the motherboard and processor, I chose the JetWay J9F2-KHDE and the Intel Core Duo T2300. I wanted a dual-core, relatively modern processor with reasonable power usage. At the time the J9F2 fit the bill nicely and so far has not let me down. Here is a picture of the motherboard with memory, CPU, and wireless card installed:
And here is one inside the case:
The C138 case has a tray where the drives are mounted as you can see here:
For the power supply, I used the 360W Opus DCX6. It is probably overkill for my application. The 90W power supply that came with C138 was able to power the computer itself without peripherals, but my power calculations with everything came to about 150W. I also wanted something with room to grow.
The Opus is a little big so it doesn't quite fit inside the C138. Instead, I bought a plastic enclosure for it. I drilled some small ventilation holes, added a 40mm case fan, and an LED to indicate status. I wanted all components to be easily removable so I bought some wire, Molex connectors, DB-15 and DB-25 jacks and created some wiring harnesses like this one:
The resulting computer and power supply look like this: