sounds like the sender in the tank is hosed. do you know how to run an ohmeter?

 

yes I do. where do I find the sender??

 

most I have seen are on top of the tank

 

I believe you can get to the sender without dropping the tank on a 67.
It is located at the front facing top center edge of the tank. Crawl under there or get the car on a lift and you'll see it.
Might want to make sure the ground wire is good to go with a clean ground.
You'll see it when you get under there.
Can't tell you how to ohm something. (my brother does that kind of stuff for me).
Tom may chime in again and tell you what it should read.

 

IIRC the resistance of the sender runs from 0 at empty to 90 ohms at full. Shouldn't be any hitches or dead spots in it as you move the swing arm from empty to full and back.

See also the excellent TechRef from Wes Vann at:
http://www.chevelles.com/techref/tecref18.html

 

Thanks, and the article was very helpful. I am going to try it out this weekend. Thanks again.