It's difficult to change from the early one-piece Girling caliper (with separate bolt-on piston housings) to the late model calipers. The mounting system is different, I believe all the way down to the differential casting. I think it can be done with a custom bridge, but I'm not positive. I don't think CWI's kit will work with early caliper design, since the basic caliper is not split down the middle.
The later calipers are much cheaper to rebuild though. $10 pistons vs $50 pistons.
