Originally Posted by james_swift

This axle might fit, but it's best to drop an email to Sheldon Brown to make sure (he'll know). You'll also need a bag of spacers to go with it. Keep in mind that 120mm track hubs typically have a 42mm chainline, so you'll definitely need to swap-out the bottom bracket. For starters, my 68x107mm Shimano BB gives me a 49mm chainline with the sprocket mounted on the outside of the crank spider. If I were to mount it on the inside of the crank spider, it would only give me ~45mm chainline. So with a 68x107mm BB and your 120mm track hub, your chainline would be off by 3mm. You might need to go with chainline spacers to compensate (not sure how far you can go before the sprocket bottoms-out against the chainstay).