I wanted to have a look at the Electrical Connection on the Sending Unit on my Sunliner because the Dash Gauge is erratic.When I took off the Cover in the Trunk Floor the Sending Unit is not there. Its forward of the cover and not accessible without dropping the Tank. When I had a look at the Tank underneath the Fuel Outlet Pipe is welded to the Tank. Does not have the usual flared outlet where You screw the Fuel Line to. Someone has added a large inline Fuel Filter at the Outlet which is fine. Probably not been changed for Years which I will do. Its a replacement Tank. Annoying that the Sender is not accessible. Has anyone run across this type of replacement Tank? An older Repro maybe?

  

Sounds like you have a 55 Ford gas tank,the sending unit location is different on the56

That makes Sense. I wonder if that's why the Gas Gauge is erratic? Depending on what Sending Unit was installed? Once the Tank is half empty the Gauge starts to swing between 1/2 and Empty and back again. 

  

Before you drop the tank, you might want to add a jumper ground wire to the tank and see if that helps the gauge.  A jumper directly to the sender would be ideal, but that is probably not possible in your car.

John - "The Hoosier Hurricane"