Interesting discussion on SS427 Facebook page. Seems a guy bought a used SS427 from a new car dealer back in 1975 or so, and it had what appeared to be "Factory rear discs" It appears it may have been a Camaro JL8 rear disc kit, installed on an Impala 12 bolt. This guy feels it was factory due to the appearance and condition of the brakes,and I could see where one could believe that. As a GM Tech in the mid 70's, I worked on a couple of 69 Z-28's that had rear disc, as I remember, nothing really special about them, I'm thinking it could have been possible to put that kit on a 12 bolt Nova,Chevelle,or Impala as an over the counter installation, but who knows. Z-28 and Impala shared the same Rally wheel, right? I cant remember how the e-brake cable assembly was routed and hooked up, that may be an issue,but it's been years since I've looked that option over. Interesting discussion, may want to take a look.