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For those that are interested in various ways to mount the Norton gearbox here is one way. It is on a racer, so the inner primary is a simple 1/4" plate. The F106 has its legs sawed off. Although this particular set-up has some modifications, I think it would work with a stock primary cover. When you make your own plates you can modify the relative positions of the gear box, the engine and the swing arm, which was done here.