Hooking up the sending unit to the gauge is as simple as one wire, however as Chris mentioned...you need a "GM" compatible gauge to go with your 0-90 ohm GM type sending unit. Some gauges are made having high ohm readings as empty, usually around 75 ohms (most Ford & Dodge that I know of) & go to 0 at full, while the GM's start at 0 & go to about 90 at full. You can probably check Autometer's website to find out which gauge you have if you have a part number. Hope this helps. Lorne