I think that since they were not built as enthusiast type cars, once they developed a serious enough problem, they were junked. When I lived in CA, they were plentiful in the junkyards due to failing a smog check. The CA government allowed a $1000 buy back for cars that failed smog check. I have front disc brakes on my '72 Duster from a Fifth Avenue car.
popular in the U-Pul it for motors trans and disc brakes and 7 x 15 steel wheels