*C7 Z51 Dust boots & pistons are different from conventional Internal Fit type (only oil seals are the same), so they are not COMPATIBLE with older models. Both dust boots and pistons are being tooled with availability be announced later.
GC7 Z51 calipers not only the boots and pistons are different, they don't come with cross-over tubes because their pistons are same size unlike BC-42, with differential bores so no orientation concern, however there is a small part that holds brake fluid from leaking out of caliper halves after assembly. See pic below.
Instead of OE's bushing, we use O-ring which is compatible with OE bushing based on our hydro test and is a better alternative in material and design.