I added an oil pressure and voltage gauge in place of the CD storage tray in the dash. I got the faceplate from:
http://www.9xauto.com/911.html I painted it with rustoleum satin black, which makes a pretty good match to the dash plastic.
I got the gauges from egauges.com.
I chose the VDO "Vision" series. Just make sure you get the stud mounting kit, as the spinlock mount that comes with that particular type of gauge does not fit in the space in the dash.
For the oil pressure sender, I got the 996 sending unit which operates roughly in the 10-180 ohm range.
- Art