[dana44]

The comparison to make is the location in the tank itself and the depth of the tank, Also have to remember there may be differences in the hoses and vent tubes between the years, which is something that can be altered without a problem with a little work. Maybe you can find a picture comparison and figure the mechanism for the fuel sending unit could or can be changed out by itself, gauge itself would will have the same voltage and ohms reading most likely.

 

[valiant67]

I think you will find the sending units are different from what I've read on another board. It seems for the late B's the choices are a used one from another car, an NOS one or having the current one rebuilt. However, I've had them simply quit working because the tank has lost its ground and running a jumper wire (with an alligator clip on the end) from a known good ground to the tank made the gauge read again.

 

[ImperialCrown]

Many times the level sender unit wiper contact wears or no longer contacts the resistance shoe. If the shoe itself is still OK, the wiper arm can be carefully sprung back to contact the shoe and you should have a working gauge again.
By working the float arm up and down slowly, you can watch the resistance track smoothly on an ohmmeter.
A good unit/tank ground is important. Just because the tank is held by metal straps doesn't mean that it is well grounded.