If you want to break 200 MPH then I would start with body mods. That stock body wont be able to go 200 MPH and stay together. You will need to pretty much rebuild the ENTIRE car. Suspension, engine, body, etc, etc, etc.
Dont do gears, cause they will make it harder to get to 200 MPH. Unless you go to something lower than the stock gears. But then it would be slower than it already is.
Basically its not a gaol for someone with even basic car knowledge. You need a crapton of money, a very good shop, and time.
Basically, 200 MPH is not a realsitic goal unless you own some racing team or something.