Also, don't forget to change the cam chain. All of the older 200's I see need seem to need a new one. This one item can prevent all sorts of trouble down the road.
I did a modified 200 with a very high compression piston in a stock bore/stroke. I added a hot cam, valve springs, big carb, big exhaust. The bike ran very well and would top out over 80MPH. If I were to do it again, I would go for the bigger displacement on a stock cam, wich would result in the extra wheelie power I like so much. In other words, my setup was lacking in low end torque, but had plenty of top end.
Chris