I'm hoping for some electrical advice. I have a '54 3/4 ton pickup that has negative ground and is 12 volts. According to what I've read, both of these must have been converted from original. I just found a fuel gauge at a wrecking yard and I don't want to fry the thing. I have a resistor, so my question is: do I put the resistor in the red line or do I put it in the black to compensate for the polarity change in the system. Any help would be greatly appreciated.