If you're replacing a 27.0mm headset, you might be better off getting your fork crown cut down to take a 26.4mm race. I think the only options for 27.0mm headsets are the steel Levin and the pricey Hatta Swan. Both are fine, but if you don't want to deal with maintaining a loose ball headset you'll have a lot more options to choose from in the world of 26.4mm crown races.