Not as large scale as that, but a few months ago I made an external HDD mount out of Lego bricks. I used a Seagate GoFlex USB dock from an external drive that I gutted. I Lego bricked it together so it held the dock and a drive could slide in and be held in place. It worked fine, but a few weeks later I re-cabled the server case and decided to add that drive as an internal SATA (it is my WSE2012 server backup drive).
You want to start a thread about that somewhere (or point me/us to an existing one), I've very disappointed by the state of car head units but I'm also quite disappointed by the state of carPCs (at least so far as I've been able to research them). I'd be curious to see what you're doing.
Bought a Pioneer Avic on clearance for like $300, and loaded new Windows OS on it. There is just no way in hell I could have cobbled one together for under $300.
Edit: www.avic411.com is a good place to start modding the hidden gem of commercially available carputers.
I wonder if I can flash my AVIC 920bt with that f/w? I've been to that site but not for a while now. Do you know if instructions to do that are there?