fuel gauge reads wrong

First thing to do is figure out if the gauges are accurate. The oil, fuel, and temp all use the same resistance. Find yourself some test resistors, and hook from the gauge wire to ground, turn the key to "run" and wait about one minute

http://www.forabodiesonly.com/mopar/showthread.php?t=179517

The test resistors are

L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full