It can be done, but I don't expect it to be easy or cheap. A set of rear-sets and clip-ons, with a modified seating area to put the pilot into the crouch, would be a good start.
The closest I can think of, is Kainzinger's bike. The read on it is a lot of fun, as I suspect is riding it. You could buy three new Gen. II's for what this would cost you.
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Here's another person's take.
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You might want to re-think the cafe racer theme and choose another performance theme, which might be cheaper and easier to realize: a short track theme, or probably more in-keeping with the size of the engine and the bike a 'miler' dirt track bike. Something along the lines of Kenny Robert's TZ750 miler bike.
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