So going to give the G Master a go. From memory the forks on this have quite a bit of thread. Here is a photo of all the bits of this most interesting headset
I have the trek m system this came with - believed to be an original option, a couple of black cro mo jobbies, a nice titanium one that came off my Klein Pinnacle when I fitted it with a MC1, or a NOS flexstem
Love that headset, looks like a quality item. Personally I would actually go with the flex stem as well, it suits the frame and decals really well in my opinion.