what great ideas you all provide! I ended up installing the front brake on the rear--the little cross bar the brake mounts on is machined flat on both sides, so no need for scalloped washers.

mounting the rear brake on the front was a little trickier. The Centaur comes with a thick nut on the mounting side, and still required a scalloped washer to conform to the stem. That combination did not allow enough of the bolt to penetrate into the core of the stem, for secure fastening. So I removed the nut altogether, and substituted the hefty aluminum block (with a scalloped face) that came with the original Weinmann center pulls. It had to be reamed out a little, because the Centaur mounting bolt is stepped. I also borrowed a thick aluminum washer from the Weinmanns and filed a convex profile on one face that conformed to the curve inside the stem.

Then I took some little torpedo shaped barrel nut (can't recall where it came from), which was short enough to fit inside the stem, and ran it tight with an allen wrench stuck through the hole in the back of the stem. Gooped the threads with a generous application of blue loctite.

even without the original nut, it feels real secure. the radiused washers give it a lot of stability, but it is still possible to rotate the assembly so the shoes meet the rim simultaneously.

It's finished off with Tektro 340 levers, and Koolstop pads--their Campy style, 1/3 black 2/3 salmon. The feel is superb. I admit it's a hodge podge of parts, so it's fortunate that I am not a purist. but if it makes you love your bike, I think it's ok.

FWIW, the Centaurs have just barely enough reach. There will be no swapping out to 700's, without changing the brakes.

anyway--thanks all for your advice. Happy riding!