Mopar fuel gauge levels:
L = 73.7 Ohms
M = 23.0 Ohms
H = 10.2 Ohms
meter your new pickup on a DMM and check against these known values. Get yourself a potentiometer (volume control) and rig it up to a DMM. Turn it and find where these ranges are and then attach it to your fuel gauge. Emulate these values again, moving the float and see where they end up. you may be able to get the range dialed in with a few inline resistors.
