Good morning,
I have an original 70 6 pack Chally. The "Coin" on the front of the"K" member has a 12 stamped on it. I have seen this (12) on several 70/71 BB and SB cars previously. My "K" member has the skid plate however my understanding is that the skid plate was not always installed on 6 pack cars but was for the Hemi cars.
I am fairly new to Mopars so I am always open to correction and learning new information, just wanted to share this.
Hope this helps.