5 volts or 9 volts, that is the question...

My dash voltage limiter has gone to the heavens in my 65 cuda. It's built into the fuel gauge and both the temp and fuel gauges read low new fuel sending unit ohms out correctly. I did some looking around on the net and found out it's a regulated power, either 5 volts or 9 volts. Anybody out there know what it is??? I've got a 5 volt chip to put in it's place but I don't want to tear up the fuel gauge until I'm sure.