Thanks hamster, that could complicate things even further.
I've refitted the original for now, the crown race was quite loose. Can lift it back off by hand.
Can anyone tell me the effect of a loose crown race?
Steering will feel "wobbly" much like ground misshapen bearings. If you have access to a blow tourch and basic brazing skills, you can always melt some brass rod on the crown race area to fill it out.
Thanks. Not sure about brazing just yet though, although it could be a useful skill.
I've been and invested in a decent set of calipers, the type with an analogue guage for the fractions of millimetres.
The old headset is a 27mm race with 30mm cups, which according to sheldon makes it jis.
The jis ones are like rocking horse poop on the web, only place I found one was velo orange in the states, but I went back to the lbs and he had one in stock, albeit a cheap one but still better than using the original.