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The OPG gauge kit uses electrical sending units for both oil pressure and engine temperature. The kit uses sending units for a 75 Firebird with factory gauges (available from most auto parts stores). To connect the gauges, attach the green and blue wires (included in the kit) to the terminals marked grn and blu. Then route the two wires through the firewall and to the new coolant-temperature sending unit (green) and oil pressure-sending unit (blue).