You'll have to change your whole front end Eldy, the later dual piston (still a fixed/sliding caliper set-up, but with two external pistons) will bolt straight up to F2/F3 forks, but not the K3 - K8 forks mate, sorry to break the bad news to you.
I might go put a set for my F2 though, (I've got some in a box in my garage) they don't work all that much better, (heaps better than the K8's though) but they do look cool! Cheers, Terry.