'65 Formula S with "factory" 727 and 8 3/4?

My 66 Dart has a 8 3/4 Sure Grip. My build sheet lists the rear axle as a code 404 and the Sure Grip as a 408. No mention on the build sheet or any of the ordering information as to whether it is a 8 3/4 or not. My guess is that in late 65 and 66 the 8 3/4's were obviously used but not optioned as such but just as a HD rear axle.