The fuel sending unit cleaned up nicely. An overnight solvent bath dissolved away the crud and freed the shaft. Unfortunately, the acetone melted the insulator spacers on the terminal posts. I sourced substitutes made of nylon to replace them.
A partial disassembly revealed the innards and some fine wire too delicate to probe further. But it is interesting to see how it operates. I borrowed a multi-meter for an operational check and it appears serviceable. The cork gasket which seals the underside of the sending unit attachment flange to the tank is too far gone to serve as a template so I will trace a pattern on paper. Hopefully all of this will seal properly without seepage or weepage when installed.
Very interesting to read you.FYI,the cork seal for the fuel sending unit is availlable at Niemoeller.They also have complete fuel sending units,but at exhorbitant prices.I sourced one made for motor boat fuel tanks which fits exactly the receiving part on the fuel tank.
If you are interested I can try to dig out the adress. All you will need to have it work correctly is cutting and bending the lever arm.BTW this applies to a 220S ponton coupe but I assume it works for other models of the period.