Gordon if you're after gauges to monitor the engine, you could install oil pressure, boost pressure, and fuel pressure and also fit a digital temp gauge for the oil, water, exhaust, air, etc. temps. There was a guide posted a year or so ago by a user named "meerkat" (I think). Great idea, fits nicely with warnings for out-of-range temps.
If you're after gauges for show, fit 5 of whatever right in front of the passenger