I've got the typical wonky fuel gauge like most others here, but its behavior is more predictable. For the first 60 miles of the tank, the needle rests squarely on F. Then from 60-120, I go from F to E more or less consistently. Then from 120 to the end of the tank (around 230), the gauge sinks well below E into the nether regions.

I've taken the sender out. A physical examination shows that the resistance coil and contact arm look in excellent shape, almost new. No rust. An electrical examination shows a resistance range from 3-80 ohms, along the range of the float arm.

Now to me, this seems to indicate that I simply have the wrong fuel sender matched with my gauge. The car's odometer works, and is just over 97,000 miles, which is ridiculous.

What if a previous owner replaced the cluster with one from a later model 140? My car is a 68, and I note on CVI automotive's website that there is a sender for 67-70 cars (676912), for 71-72 cars (687826), and also for 73 cars, and another for 74-75 cars. The latter two wouldn't have gauge clusters that fit mine, but there are two sender choices for my dash years, and thus two cluster choices. If each sender had a different resistance range, then coupling a cluster in my 68 from say, a 71, would match an inappropriate resistance range with the fuel level gauge.

Can anyone confirm that the different sender years differ in resistance ranges?