Haven't seen this on a duster

...like the air dam...has to be custom made ?

Air dam is a Direct Connection piece. Counterpart to the "ducktail" style rear spoiler that was made by DC back in the day.

That car's been on eBay at least twice before. Doesn't appear to have changed hands, not sure if it "sold" in the last auctions though.

I can't believe they left the bumpers stock. Compared to frenching in those tail lights or adding the side scoops changing out the bumpers is a piece of cake. I swapped the rear shock bumper on my car for an earlier piece in a few hours.