I think I'm in the minority in this view, but I'd keep it as an 850. They lose a bit of grunt, but an 850 revs better, is less lumpy, and doesn't have bodgy turned down spigots on the cylinders to make them fit the crank cases.
bore the crankcase out to fit spada barrells/pistons.
stick a P3 cam and use the T3 carbs.
skim the flywheel by a about 1/2 off
does everything nicely












