How many of these cars decked out with aftermarket gauges really need them? Unless you're going racing, none of our engines really have to work that hard. Don't get me wrong, I'm not anti-information, but even my factory-equipped gauges tell me exactly what I'd expect 99% of the time.
One time I found a temp gauge somewhat useful was while driving my '73 Imperial cross-country around 2007. A corroded freeze plug started leaking in the middle of nowhere and the temp started climbing. For many, many, miles I'd overheat to the point of steam then cut the ignition and coast as far as I could in neutral or down a hill. The temp gauge at least showed I was cooling a bit every time I'd do that, but then I'd just overheat the thing anyway. Finally I stopped in a little town and bought some JB weld (luckily this wasn't one of the super hidden plugs). I ate dinner, let it cool and put on the JB. Refilled and never had another problem with it, probably drove another 1000 miles home. Last I saw it lives in Europe now.
So what was learned? The gauge was useful in that extreme situation, but you can pretty well overheat the piss out of a 440 and not ruin anything. Pre-ignition ping meant more to me than the gauge, that was my real indicator to shut down.
I once had a real hooptie of a '79 Dodge Magnum with a 318 that I'm sure was treated poorly long before I owned it. No doubt the engine was pure sludge. When it was cold, the engine showed decent Oil Pressure on the gauge but after I'd run on the X-way, and stop at an exit ramp the gauge would drop way down and you could hear a very light knock at idle. It lasted that way for a very long time until I bought a better car (and still sold it for for $750).
Lesson leaned? As long as you're not holding 1st gear till 70, or other obnoxious crap, even a very worn out 318 will run and give you a bunch of indicators before it pukes any parts. RBs, LAs & /6s aren't considered exotic, delicate engines.
Do I like having full gauges in cars? Yes. My Imperials, and my old Dodge truck all had them. My RMB has a gas gauge and an ammeter that never moves because they improved the charging system by '76. But would I ever bother to add aftermarket gauges? Not until I'd perfected every other part of the car, which essentially means never. I know there's enough limp-home in the car that I won't die in the wilderness or ruin an imaginary aluminum head.
I'm just saying.