The 71-72 GSX’s were not downgraded to anything. In 71 & 72, the Option was still the same as it was in 1970. The only difference was in 70 the “option package” was all or nothing, while in 71-72 it was “a-la-carte” with your base GSX option and other options as wanted. It was just a different way of ordering the cars. You have to remember that over the Spring of 1970 the insurance companies skyrocketed their premiums. At that time it was almost the same cost to insure a performance small block as it was to insure a big block the year before. By offering small block versions you could get the same bold look, but could still afford the insurance. (I have an article from that time period questioning if there were going to be any “Super Cars” in 1971.) The low body numbers were only used on the 43437 body style, and only at the Flint Michigan plant. That plant was run by Buick, all others were run by GMAD, General Motors Assembly Division, and I have no idea how they tracked SCO orders. Duane PS, a lot of guys like the 71-72 cars better because they were all different, with different option loads. Ya know, like all the 70 Yellow cars look the same and so do the GN’s. That same statement could also be why some guys like the turbo cars better then the GN’s, because they were different.