Stop in for a cup of coffee

So full is accurate I bet? Mopar full is about ten. Not much you can do really to make the full range of the gauge work I am thinking a aftermarket set up or a newer Mopar gauge if that is a Mopar sender. Also that sender is set for a gauge at 5VDC, not sure what yours runs on now does it have a limiter like Mopar does? and if so what is the output and what should the gauge be using? Lots of variables, not like you can just add resistance to work over the full range.