Just ran across this thread - Here's was my solution:
Oil pressure and water temp in the overhead console. Remove the "sunglasses/garage opener" tray and install a couple mounting cups. IIRC, I did not have to modify the mounting cup or the supplied mounting bracket. Fair warning: I'm not sure how well this works with a factory mirror. I use an aftermarket auto-dim mirror mounted to a tab that is glued to the glass (the bottom edge of the gauges is still visible at the top of the mirror, but I can see out the back window just fine).
Voltmeter: In the useless "pocket" beneath the cigarette lighter. I did have to shorten the cup, and make a custom mounting bracket (lower profile), so that everything would fit. I prefer the voltmeter down there, because even dimmed it is bright.
That leaves the A-pillar for 1 more (I put my boost gauge there).