The calipers are the same from the K0 to the K6
The K0 is silver but theĀ caliper is the same as the K1-K6(black).
Note however the arm ,that the caliper bolts on to, changed from the K3 onwards and was the same up to K6. The K0-K2 have the same arm.
The F/F1/K7/K8 used a different type of arm as well as caliper.
If you used both arm and caliper from a F/F1 series it would work on a K6