Sample Guage Pod (not mine as outlined below)

Guages really aren't that hard to install. Below are my instructions for installing Oil Pressure, Temperature, and Voltage guages.  If you already have the guages, you have the installation instructions that came with them too.  I made three sets of wiring harnesses. One set for the guage lights, one set for the guages themselves (both of these harnesses reside in the a-pod itself) and a third harness that is inside the dash board. On the set for the guage lights that light up the guages, I wired the three light harnesses in series so that at the bottom of the guage pod there is only one white wire (positive) and one black wire (ground). These two wires have 'male' connectors crimped to the end of them. The dash harness (the harness inside the dash) has a white wire and a black wire in it, with female connectors that come out of the dash near the base of the pod. The white wire goes to the wire that lights up the bevel around the headlamp switch - remove the dash trim and headlight switch to get access to it, then tap into it using a quick connect similar to what you would use to wire in the harness for trailer hitch lights. This is what gives power to the lights in the guage - it also allows them to dim with the dimmer switch. The black wire goes to a ground bolt that already had a couple of other grounds on it - it's located near your right knee, under the dash board.

The second harness in the guage pod is for the guages. All three guages have a power and a ground. The power wires on mine are red and all connect at the bottom of the pod, along with a single pigtail that goes to a male quick connector. This quick connect powers all three guages. The ground wires are set up the same way. All three run to the bottom of the pod, along with a pigtail that leads to another male connector. There is a single blue wire that runs from the water temp guage to a male quick connect and a single red and white wire that runs from the oil pressure unit to a quick connect at the bottom of the pod. That's all the wiring for the guages. The volt meter is hooked up just by virtue of having a power and ground connected to it.

In addition to the first two wires mentioned in the dash for the lights, there are four more wires for the guages themselves. One for the power, one for the ground, one for the oil pressure sending unit and another for the temp sending unit. They all have female connectors where they come out of the dash. The single power wire goes to the fuse box under the dash. Go to Radio Shack and get a 'fuse tap' and tap into the radio fuse - that will give the guages switched power. Run the ground to the same place as the ground for the lights. The last two wires, for the oil pressure and temperature sending units, need to go through the dash. I fed a coat hanger through where the spedometer wire comes through the firewall - from the engine compartment side. Connect the sending unit wires and pull them through with the coat hanger. Run them to the sending units.

To properly install the sending units, go to Lowes, Home Depot, etc. - to the plumbing department and get a nipple and a 'tee' for both units. Take the sendign units along with for sizing. The tee will allow you to keep the stock sensors for the computer and dash board guage and idiot light.  

That pretty much covers it.  Study the instructions that came with the guages, study these instructions, and you should be able to figure it out.  Good luck!

This is a close-up of the harnesses.  The top harness is the one for the lights that light up the guage pods. The bottom image is of the harness for the guages themselves.

This is the whole harness that goes in the pod.  Again, the top one is for the lights, the bottom for the guages.  I don't have a picture of the third harness, which is located in the dash.