I still have the original sending unit. It never stopped working; I just thought it would be a good idea to get a new one when I replaced the tank...
Some sending units come new off. Like what happened to me and my 67 mustang. Over on the mustang forums they said I could bend the float to get it in range or add a "module" that adjusts the ohms. after the PITA it was to get the tank out and put a new sender in, I was going to put a resistor or module in and adjust it that way. Sadly this time last year I was forced to sell the 67. Miss her.
Got the car home and tagged yesterday. Runs pretty good. Has about 6 gallons in it, but shows around 1/4 tank. Need to fill it up and see where it hits.