Years ago I mounted two 52mm's in the ashtray location. I trimmed the circumference to make it slightly bigger, made a leather, black template for the ashtray hole that would fit the two gauges and that's about it. I would post pictures, but my car is getting some work to it right now, so I can't snap any just yet... maybe next week if anyone is interested.
I am redoing my gauges pretty soon however... I'm going with Apexi EL gauges in a duel pillar pod and will put two new gauges in the ash tray location. The attention the pillar pod will attract is a slight concern, more so parking down town... I had my Xterra get broken into because I had change in one of the cup holders - F'in crack heads. I'll just have to park in a garage from now on, but I'm not going to let a couple of crack heads stop me from building my car the way I want to.