I was thinking 9v was just asking for a burned out gauge but that was what the fuel gauge needed to work properly on the bench. After installing everything and driving the car a couple times, I had to turn down the voltage regulator because the temp gauge was reading full scale with a hot engine and 9 volts. I haven't put a meter on the regulator to read voltage yet but I'm guessing it's in the 6 volt range based on where the pot is adjusted to on the regulator board. As a bonus, the fuel gauge started working better at some point after the adjustment. Not sure what that's about but I'll take it.