Welcome, don't know about LED assemblies but there is a few site that sell LED replacement bulbs for autos, make sure you get the ones that have the widest light pattern so the LEDs will reflect off the reflector like the standard bulbs do. You will need to change the Flashers to ones that will work with LED lighting as the factory flashers will not see enough load to flash properly unless you wire in a load resistor for each LED bulb.
Also 70 and 71 dusters have the same tail light style, the 72 tail lights are also similar but wider horizontally compared to the 70-71 style.
