Fuel gauge. Again.

I've read that this topic has been beaten to death but I'm still in need of advice.

Fuel gauge in my 67 Dart reads just under half on a full tank and quickly drops to read empty when less than half a tank is used. Sending unit float flooded I thought. New sending unit in and same thing. Old unit appeared within acceptable tolerances actually, little off, so I replaced it anyway since I had a new one.

Checked at tank with a test light. Solid pulse. Grounded sending unit wire failed to make gauge do anything but go to a little over quarter full.

Temp gauge works fine. So I'm thinking gauge itself unless anyone has any other thoughts.

Thanks in advance. Appreciate your guys input!