I just got a 66 5 gauge dial cluster and am going to get it installed later on, in my 65. For now I need to check if it works, at least the gas and temp meter. Is it possible or will I have to wait until all 5 gauges are connected to see if it works? ::
To check it, you need to have a CVU (Constant Voltage Unit) attached to the back. It may or may not have come with the dash assembly. It's the little device that converts the 12V coming in down to 5V that the gages use. If you've got that you can hook it up like the wiring schematics, and hold the final connection to ground and visually watch to see if the gage deflects. If it moves from left to right, then your gage is working fine. This works for the Oil, Gas, and Temp gages. Ammeter is different.
You need to go buy the Jim Osborne wiring schematic for your car. Its a good investment (less than 10 bucks) if you're going to do wiring modifications.