I cannot find a wire to go to the gas tank for the guage. Which harness is it suppose to go though?

What year of CAR???

Generaly it's the tan wire coming from the tail light harness passing through the trunk floor right behind the license.

Read this post for some pics
http://www.chevelles.com/forums/showthread.php?t=93013

I have a 67. There should be one wire that goes to the tank. Now I have seven wires in the harness going to the rear. However two go to the dome light two go to the back up lights and three for the brake and signal lights adding up to seven. I also am not sure what wire or wires are for the trans to operate the back up lights. Originally this was a "Three In The Tree" car. There is some type of a swith on the top side of the column down by the firewall. ???? Don't know as I bought the car with many parts missing. Any info would be greatly appreciated.

Thanks
Kevin