hi JakeM,
i would encourage you to pursue keeping your truck original and finding a better gauge or fixing an original one.
they are only original once
I have not tried swapping the fuel gauge, but i have fixed them and studied their design, from what i can tell an OEM fuel gauge should work either polarity.
So the aftermarket one you got is doing something more modern inside if it can't work for your situation.
The OEM design is two electro-magnets in a balancing act, swapping polarity swaps both the magnets, they should still perform the same balancing act unless something less intuitive is going on that i'm not seeing at the moment.
best of luck
-s
