If I bought a set of road wheels made for an 9 or 10 speed cassette in the rear could I convert the back wheel to just a single fixed cog or even a flip/flop or would have have to get new hubs as well? The front wheels are interchangeable between fixed and geared no? I'm asking because of this set I found on Ebay. Looks like a nice set of wheels for good money, but not for fixies. Mavic Open Pro Shimano Ultegra 6500 Wheel Set 700c Black Road Race Bike Wheels | eBay
You can buy a New Set of Track Mavic Open Pro's with some Formula Sealed Hubs, for about $30 more shipped. It will also have a flip flop hub and you should be able to get it in rear spacing of 120, 126, and 130mm.