If all goes to plan, I want 2 gauges, 1 tweeter, & if space remains, a GPS. I plan on using 2 1/16" digital (imagine that!) gauges. I'll add a single tweeter on the passenger A pillar as well.
The only problem I foresee there is the GPS, unless there are units out there that come with (or have available) a 2.063" adapter that clips to the back. This is the case with most of the diesel tuners we sell. It's a great place to put something like that.
If you do some digging around, there are ways to invent your own digital gauges.
Auberins.com has a gauge they sell primarily for EGT, but with the right senders it can be used for any number of engine parameters including pressure, temp, volts, etc. It has a programmable high/low warning with a relay output, too. Engine gets too hot for your liking, it can override your electric fans. Oil pressure too low? Cut the ignition or an electric fuel pump off. If a guy's feeling ballsy, he could open it up and put the display in his intended spot with the remainder of the electronics elsewhere, including the control buttons and warning LEDs. The display itself is small and would be easily placed; the unit's face is 1/32 DIN. The numeric display is available in 5 colors: red, blue, green, white and amber.
In the case of the cluster I'm using, for $20 they'll put turn-signal & high-beam indicators in the speedometer, so I decided that the original spot in the Mirada cluster would be a good place for a digital volt gauge (gasp! digital!). I ordered one off
Amazon for less than $7, also available in red, blue, green, or white. Blue & white are a little more expensive. It's small enough to fit in the existing hole. There are also amp gauges like this that come with a shunt (they cost more, obviously) but the temp gauges I found did not read high enough for automotive use.