i think you'd be disappointed to learn how standard a 'factory' or 'works' bike was.. there is an article in the contemporary press outlining the differences between a standard cub and the bike that had just won the welsh two day trial.. steel rims and all.
much prefferable to have a rideable/ useable bike.. wide swing arm, electronic ignition, c15 or hd forks, alloy rims and modern controls would be all that you d need to have a very usable classic motorcycle that was easier to ride and maintain than a period 'works'/'factory' bike...