1968 barracuda temp gauge and fuel level inop

I mentioned a 27 ohm resistor as that is a value Radio Shack might have in stock It will be close enough to give a reading on the gauge close to the center. Stock resistor values run 22 and 27 ohms with 10% tolerance resistors and there is a 24 ohm 5% value as well. Radio Shack is unlikely to stock any thing other than 10% values.

The readings you measured with your meter on the temperature sensor line are very low and I suspect so low that there really isn't anything there.