[AtomicLabMonkey]

The big decision is mechanical gauges vs. electrical... mechanical ones actually run capillary tubing inside the driver's compartment right up to the gauge on your dash, and the capillary tubing is filled with whatever fluid you're measuring, oil, water, etc. This means you have hot oil & water in lines under your dashboard... up to you, and I've seen plenty of people do it on street cars, but I myself am shying away from that for street use due to the potential leak they represent. Electrical gauges have a sender unit under the hood hooked into whatever line or engine part you want to measure, and then just run an electrical wire inside the driver's compartment up to the back of the gauge. The thing that's nice about mechanical gauges is that they have full-sweep (270 degree) readings that are nicer and have more precise markings than most electrical gauges which are only 90-degree sweep. You can find some full-sweep electrical gauges however, they're usually just harder to find and I think might be more expensive than standard sweep electricals.