The chrome covers were an option, unless the chrome cover box (engine dress up kit?) was checked when the car was ordered, the car didn't come from Mopar with the chrome covers.

I suspect the dealership ordering the cars had a lot to do with if the car came with the chrome covers or not. I highly suspect places like Grand Spalding Dodge or a high performance Chrysler/Plymouth dealer ordered a lot more cars with chrome covers then my local Dodge or Chrysler/Plymouth dealer ever did, our local dealers probably didn't even know the chrome cover option existed. Gene