Where can I find a set of pistons to hop up an O-200?

Answer: John, use stock C-85 pistons. They are 3/8" higher than O-200
pistons and will give you that "pop-up" effect, that is, a little higher
compression. Not legal, of course, in a certified aircraft, or aircraft
engine you plan to leave the data plate on.

For more secrets on blueprinting and tuning the O-200 for speed and power,
see the guys who race them at Reno.