Sorry to take so long to reply, i have been trying to contact some local Goldie owners and without phone numbers and crap weather the scene has been quiet.
However i managed to to contact 'Dinger' and mates who i run into occasionally at a midweek meet they appear in this film:http://www.youtube.com/watch?v=U2ppHf-EG8o
Dinger has owned his 350 from new and he told me tonight that his TD yoke (purchased in 63) fitted tight with the castlelated nut, after some time the alloy yoke started to wear on the bottom edge on the stem hole against the steel nut. He now runs the yoke with it machined out and fitted with Bronze bush.
In summary, if your yoke has a larger hole then it has been bored out at some point. I am referring to the early yoke, which is sand casted and has the words Taylor Dow and Superleggera. Later RGS yokes were different!
Your locking ring is the way to go as per the original kit, i am probably going to bore out the hole and fit a bush if not go with your idea.
I am going to post to the other Dave as well.