All had drum rears until 79', then you had to get the WS-6 package to get 4 wheel disc. Same in 80' and 81', only WS-6 cars came with discs all the way around. I guess in theory you could have ordered 4 wheel disc as an option without the WS-6 package beginning in 79', but I have yet to seen one that was not originally a WS-6 car. If someone knows of one then let me see the build sheet proving it, I'm not saying it didn't happen. The option code for 4 wheel disc was J-65 on the build sheet and WS-6 of course was a separate option, but automatically came with J-65 code brakes.