I have a 69 Coronet that I replaced the sending unit and tank. The gauge will only read half full. I have filled her 3-4x but she won't budge. I thought it was the ground and put it back on last night, but no luck. I was told I might have the wrong sending unit. Will I run out of gas when the gauge reads empty? Thanks for the feedback.

 

if you have gas in the car, dont worry about the gauge
it might just be a bad sending unit

 

http://auto.howstuffworks.com/fuel-guage.htm follow the "next pages". Guess its better than reading half empty!