I'm sure this has been talked about a few times but I wanted to share what I had found out about the fuel tank sending unit in my 93 F250. I know the sending unit are almost impossible to find but I was lucky enough to get of in unknown condition at a junk yard for fifteen dollars. I removed it from the tank and notice that the float was slightly full of fuel. I removed my tank to fix my sending unit (it hasn't worked in a year lol) and I found that my float was also partially full of fuel, making it heavy and causing the gauge to stay on E. I was able to find the pin hole and solder it up and know everything works the was it should. It was a very easy fix (kinda). So if your gauge reads E all the time you might have the same problem!
I also purchased and replaced the plastic/rubber suction screen on the end of the sending unit so I shouldn't run out of fuel at a quarter tank!

 

^^^^^ That's ALWAYS the FIRST thing to check with an inop sending unit. VERY easy test, once you get the tank down, or the pickup out of the tank from above. Just switch to that tank, turn the key on, and work the arm with your hand. If the gauge needle responds, sending unit is GOOD and the float is the prime suspect.

Replacement float is about $5, by the way, and as you found out, just snaps onto the arm. Hole in mine was so small, it took months to "regress" from normal ops to full inop. And when I removed it, no matter which way I turned the float, I could not get the fuel to drain out. I suspect it was a VERY small breach of the seam. So I just replaced it. Obviously waaaay cheaper than the sending unit itself, and easier to find, and probably accounts for a major percentage of the inop sending units out there.