Lug size on a 72 Dart?

1970 was the very last year for Left hand threads on the studs and nuts.
Anything else other than that, is just bull ****, and an old wife's tale.
Have no clue about your 72, but it DID NOT leave the factory assembly line like that.
Well I will need more than your word on this, I have had PLENTY of 71 and 72 Demons with left hand threads on drum brakes and disc brakes, one was a 71 SURVIVOR with less than 3000 miles on it with left hand lugs. Please show me the TSB that states that it ended in the model year 1970...