Answer = a.

I was in more or less the same position a couple of years ago with my '72 Paramount, but the wheels had tubular rims and I wanted 700c clinchers. I took the plunge and bought a Spin Doctor Truing Stand and a Park Tool Tension Meter, and downloaded the e-book Professional Guide to Wheelbuilding, by Roger Musson. I used my original Campy Record high flange hubs, and laced them to Mavic Open Pro rims using DT Swiss stainless 2.0/1.8/2.0 double-butted Competition spokes.

It was one of the most satisfying experiences I've ever had, and I've built several more wheel sets since then.