Hi Mark,
I'm no expert on this model but whatever the ratios were when it was built will not be the same now. Modern fuels and synthetics oils are much more efficient with less smoke etc. As a start point I would suggest a 50:1 ratio, which is 20 ml of oil per litre but I would suggest you contact these people who may be able to give more informed guidance:- http://thetwinshockshop.co.uk/index.html
The bits on your forks, could they be for attaching a competition number plate?
Cheers.