not so accurate guage

I don't know if this helps, but I am having the same problem. I have an autometer fuel gauge, 73-10 ohm range like the factory, with a replacement sending unit that is also 73-10 ohms. However, mine shows full when full, then sharply goes to empty, with about half a tank left, like yours. When I called Autometer's tech line, they said that the original sending unit was not a linear resistance throughout the travel, meaning it was not 41.5 ohms at half tank, and this is how they designed their gauge, to work with the factory unit. He said that most new repo units are linear, which is why they read right at empty and full, but not in between. I haven't dug too deep into it yet, but it makes sense in my world. You may also have the same problem. Can anyone else elaborate?