If you aren't building a track-only car and don't need multiple gauges displaying simultaneously, P3 makes a multi gauge that fits in your AC vent. It runs off the OBD port and looks dead simple to install.
I don't own one myself but got curious about it after seeing it in @
ImperiousRex's build here:
http://www.ft86club.com/forums/showthread.php?t=28008. If it's accurate and can auto toggle the display based on peak warning thresholds then it could be a solid solution for street cars seeing track use.
The dumb thing is they don't have a user manual available for download. It would be good to see the exact capabilities and limitations.
More info:
http://www.p3cars.com/subaru-brz-sci...tal-interface/