fuel guage problems... about ready to give up.

[67chevy1series]

well heres the story. when i finally started to drive my truck i realized the fuel guage wasnt reading properly. so i took the original sending unit to the tank out and put a new one in. this one was a reproduction made for a 72 (has vent tube) so i put that one in and it didnt read right either. so i replaced the fuel guage. still didnt read right. so i bought another new sending unit that is a reproduction for a 67 (has no vent tube) this one worked for 3 days maybe 2 after i put it in. one morning driving to school i stopped to get some gas. i put 20 bucks of gas in and then turned the truck on and realized that my gauge started to read empty... so i was thinking how i could fix it, and thought maybe its the little resistor that goes from one of the metal studs to the other, on the back of the guages. so i replaced that with one that looked perfect, and still my guage read empty... so i kept driving and i noticed when i made turns it starts to read but once the gas in the tank levels it reads empty again. so i figured out that the little brass float in there was full of gas and just sinks. so i got another one and i submerged it in water to see if it would fill up with water or if it would float. it floated every single time i submerged it. so i figured, ok this ones good and i took the sending unit out of my truck and put the new brass float in..... STILL DOES NOT READ!!!! it still says empty!! and my wire is fine i checked the wire and it has no bare spots or anything im getting really tired of this and i am out of ideas and im just about ready to let the truck win the battle. PLEASE HELP ME.