Why what? The above posts tell it like it was back in the day. SAVE MONEY and don't care about anything else. The change from the 70-71 side marker lights saved .50 per car, by going to the ugly sticking out 72 and up side marker lights.
Changed many a car to different model - year - combination my copper car is a 74 Scamp with 69 Valiant front clip 71 dart rear bumper etc made a 71 demon out of a Duster on and on just wondering why asking about taking body off the unibody sub frame