my 75 dart and the valiant wagon and the 72 duster all have issues with tail lights.
For some reason they don't repop tail lights for a 72 duster yet every other year of duster has re-pops available.
I don't have anything for a tail light for the 72 duster, I am tempted to change out the tail panel to the 70/1 type because those lenses are available new all day long.
I got lucky with the valiant wagon because I found two pair of NOS lenses and it makes it easy that the lenses are the same for either side ...simply flip it over and you have the lens for the opposite side LOL
the 75 dart, I have not addressed it yet ...I guess the solution is to buy up a crap load of used lenses and see which one work the best.