Travis,
Do not get too alarmed if you do not find a vibrator on the back of the guage like a beetle speedo. Only the last year or so had vibrators, I believe it was only '74, but I thinks some late '73's had them.
My' 69 doesn't have a vibrator and my gauge moves around a lot when I drive.
For the 1st few 200 miles or so, my guage didn't work, I checked the fuse, checked the continuity of the wires to power and to sender and nada.
Then after about 200 miles the guage went to 1/4 then 1/2 tank after a few tank fulls of gas, that stayed for about 6 months, then bamo about 4 months ago it just started working.
It never gets quite full, but it is way better than it was, my idea is that the caramelized gas was stopping the float from moving in the cyl.
I know you said you checked yours, but might be worth a look again.
If you use a vibrator, I bet you can use a regular beetle sender in stead of the crazy ghia tube one...
KC