fuel gauge not working properly

what i have is a 1973 chevy k10 pickup. the fuel gauge was stuck on full it was actually past full around 3 o'clock or so. so i dropped the tank tested the fuel sending unit it was bad i got a new one. i checked it again after i put the tank back in it and the gauge wouldnt move so i got a new one thinking it was the gauge it self. that was not the case. i set the gauge to empty and put it in the needle began to rise (key is off) went all the way past full. i put it back on empty and it started moving again (kill is still off) then i turned the key on and it stopped, i turned the key off and it continued to move. my ignition is messed up and have a new one to put in but havnt yet i dont know if this could cause a problem or not. please help