Jason,
If you want to know the details of what to measure, etc., read
http://www.allfordmustangs.com/forum...s-how-fix.html That may be too technical for you but I do give the resistance values, etc: 73-10 Ohms.
It might be your sender, it might not. If its only the float that is an easy replacement. With the wire off the sender if you still measure 73 Ohms to ground through the sender it might just be a float problem? I agree that the Ford sender is the best if its still usable. Turns out my car had so many bazillion miles on it that the little brass pad on the end of the sender potentiometer in the tank had completely worn away from sliding up and down every time the tank sloshes. Although I did 'fix' it as the above thread describes, the fix only lasted for a week or so and then I was back to where I started. The 4th picture I posted shows the internal contact and there is a brass pad mostly missing on the right end. If that is gone your sender is toast.
New Ford senders are disappearing if not already gone so I bought a new repro which turned out to be Scott Drake when I opened the box (their stainless, 5/16" version). As usual, I have mixed feeling about it. It has a 5/16" pipe like the original while most of them still have the 3/8" pipe used for '67(I believe?) and later. They also haven't figured out how to mount the pipe though since its bent at the wrong angle and almost prevents you from attaching the boot on the sender's external connection post. The float is also set about 1" too high so unless you bend it down the gauge reads zero until you have about 7 gallons in the tank making the gauge pretty useless.
The winding also isn't truly non-linear like the original Fords; picture 3 in the referenced thread. I was ready to send it back until I figured out the winding is composed of two linear windings of different pitch attached in series to make a piecewise linear approximation of the resistance vs float position instead of the original almost logarithmic winding. If you get it adjusted correctly its almost as good as the original although if they had just made in LIKE the original it would have been much better. It pegs out the gauge at 'F' about 3 gallons early which is about a gallon of so before the Ford unit did the same thing. Its physically impossible to measure the last gallon or so using this type of float since the float diameter causes it to bump into the top of the tank before the tank is full.
Not having measured one of the recently departed Ford senders I don't know if the ones from recent years were still wound like the ones from the 60s or not. Its possible the winding in a 90s Ford sender weren't truly original but similar to the one in the Scott Drake one I bought.
Need help figuring out fuel gauge not working 
The reproduction sending units frequently don't work straight out of the box. If you still have the original Ford sending unit, odds are, there isn't anything wrong with it. It probably just needs a new float. The brass floats cost like 8 bucks. Again, if you still have it, try this. With the wire attached to it and the key in the on position, ground the front of the sending unit out on the car and then push the arm with the float on it all the way up. If the gauge pegs, you just need a new float. 
Occassionally, it actually is the sending unit itself that fails, but, on cars that have been driven periodically, and the gasoline didn't just sit there for twenty years turning to varnish, it's far more common to have the problem turn out to be the float. I'm pretty sure that NPD still has Ford fuel sending units, but they are the post-68 units with the 3/8 outlet tube. 
