Barn find 72 340 duster

That's good investigative work. Does that mean that the dealer applied the undercoating or did the different assembly plants have different procedures?
Well the factory always applied the undercoating in the wheel wells at the factory. You could also have the whole under body done at the factory the code was j55? That's off the top of my head and might not be the right code. Anyway, that option included full under coat and an insulated hood pad. you could also have it done at the dealership and this is always easy to tell because under body is coated heavy and over spray on all undercarriage items and there is no code on fender tag or broadcast sheet. My Duster just had the standard under coat in the wheel wells but this is done quickly with little concern by the employee that it is blown over other parts of the car. The front inner fenders are done with the most perfect pattern but the rear on the passenger side was blown over the side of the spare tire well but not much on the driver's side of the spare tire well.
Once i get the sheetmetal repairs done will get the car on body roller and will better be able to tell what items were installed before the factory sprayed the wheel wells so i can duplicate the over spray patterns...