Hub spacing is 120mm same as a standard road bike, on the newer ones anyway I'm not sure about old old ones. I got my ambrosio hubs of ebay for 45. The whole thing cost about £150 - £200 tops. Run it without a brake, but when you start riding it really fast and weaving through cars and traffic jams, which you will start doing there's no avoiding it. You will probably have to get one Sizing, I went into my local bike shop name dropped Campag record components, carbon frame etc... and said "Can you help me identify the correct frame size" they were more than eager to help. Beyond that its up too you, track frame of ebay, or an old road frame with the inward facing horizontal drop outs. There is a big topic on OTN about fixed riding and of course there is always a font of information to be found on Sheldon Brown (rip)