Keep in mind that the very irregular shape of a Pantera fuel tank just does not allow a linear charting of fuel level even with the stock components. That inaccuracy would remain no matter how or where you installed a “corrective” resistor.
I run a VDO fuel gauge with the stock sender. The low fuel connection on the sender has been connected to a small LED idiot light on the console.
There are commercially available devices that purportedly allow you to establish multiple set points and gain a more accurate gauge reading, but in reality with our tanks you would have to start with an empty tank and add incremental amounts of gasoline to establish your set points.
I understand what you are trying to do, but in the real world I do not think it is really that important.
Whatever sender and gauge combination you have previously been using was always inaccurate and you got used to it, right?
My 2¢
Larry