I do not recall what the springloaded clamps are that grab onto the fork tubes are called but I would think your old smaller ones could be changed out for the newer larger diameter. Just loosen the four large allen headed screw a little and it should be as simple as off and on. Let me know if you need more assistance or photos.
As far as using your old clamps, I'm not sure. I've never held a set in my hands to see the difference from old to new. Your HD dealer may could help you here.