The fuel gauge is always kind of a pain with a replaced sending unit. You might have to bend the float arm on it to get it where you want. Have you tried a different temp. sending unit? Know that there are those senders made for lights and those made for the gauge. Electric oil gauges are what they are. If it reads something it's working. Even in new cars gauges will read above or below the full or empty marks. The old stuff kind of is what it is and is never going to be perfect. I take it the tach is working? I would be super happy with that if everything else seems to be working.