Hello.
There will be a wire that comes from the instrument cluster voltage regulator on the back of the instrument cluster that supplies power to all three gauges.There is also a wire coming from each of the appropriate sending unitsI believe that the sending unit wire goes to the left side of the gauge and the power wire goea to the right side, but I'm not sure about that.If you wire them backwards that will make them read backwards but won't damage anything.On the instrument cluster voltage regulator you should have a wire coming from the ignition switch, a ground wire and a wire that splits of to three female connectors.I think it's still a green wire with a black stripe in the 68s.Hope that helps.
Need a little help installing electric gauges? 
