Gas Gauge Problem - maybe incorrect sending unit

Does anyone have experience resolving a sending unit / gas gauge issue? The gauge would not read above 1/2 tank even when full with gas. Pulled the sending unit and measured the ohms - Empty 220 ohms, Full position 34 Ohms. Shorted the lead from the gauge to ground and the gas gauge then read full. Moved the sending unit till the gauge read empty and measured the ohms and got 180. so the gauge needs 180 to 0 sending unit and the current sending unit is 220 to 34 ohms. I am not sure if this sending unit is original or even if the tank is original. The car is a 1934, but has been converted from 6V to 12V. Does the change in voltage effect the reading of the gas gauge? I have not been able to locate a 180 to 0 ohm sending unit anywhere. I can find a 0 to 180 ohm GM unit, but that would read reverse from what is required. The old Ford and Chrysler sending units were 70 to 10 ohms. I tried the 10 ohms, and the gauge reads 3/4 full. Any ideas? Any sources for a 180 to 0 ohm sending unit?



BST RGDS

GARY ( happychris )