Replace gas tank and sending unit or not?

72Plymouth said
My gas gauge reads empty, then I fill it until the pump clicks off, and by then it overflows. It only takes about 6 gallons from empty until full. I know that it holds more than that. Maybe there is really half of tank left when the gauge reads as empty. I'm almost certain this is a problem with the sending unit correct? Could the current one be fixed or is a new one the solution?

Also, would you guys recommend replacing the gas tank if I am going to rebuild the engine? I just didn't want any crap that might be in the tank to get into all the new stuff. I know the fuel filter is there but wanted opinions. The original tank looks good other than some light surface rust.

My 72 Duster had the same issue and I pulled the sending unit and found the sock was deteriated and the float was full of holes which is why my sender wasnt working.I also found alot of rust in the 1 barrel carb float bowl when it had the slant six in it so im planning on either just getting my current tank cleaned or get a new one.SOmetimes you can just get a new float and sock for the sending unit and it will work again,but its much better to just get a new one and not worry about it anymore.:-D