I have recently finished installing a couple of gauges. I took took a fair bit of modification to fit the gauges where I did, but I'm happy with the result.
I have a air/fuel ratio and transmission temperature gauge with plenty of room to fit another in the middle. The AFR gauge was easy. Earth wire, power wire (spliced the cigarette lighter) and then splice the purple wire on the ECU. Still need to finish the wiring for the temp gauge. Main hold up is the sender unit works best when mounted into oil pan. My transmission is in need of repairs, so I'll get it done then.