As stated there's a HUGE diff between 150 and 200mph.. most cars (with the governor disabled) will go 150.. very few will go 200. why? Simple, aerodynamics plays a huge factor as you go faster and it's a linear deal.
Going an extra 50mph (from 150 to 200) is not just 25% more difficult its WAY more difficult. Also, at that speed air control (no just cutting through the air but directing the air properly) is a life or death thing. If you caught air under you car the wrong way at 200mph you car would become a plane and then a bulldozer.
Also, the amount of safety equipment you would need to have any hope of surviving a mishap at that speed is substancial. Anyone want to do the math on what forces are involved when a 3500 LB object is traveling at 200mph and hits something?
200mph is hard to do in an aerodynamic car like a new Camaro or Vette. It's a LOT harder to do in something like your Chevelle. Not to say you couldn't do it, just that it will a lot of work. Still, it's a fun goal.
Oh, and I won't preach to you about going tripple digits on the highway since I've done it myself. However, it really is a stupid thing to do and one mistake, even by someone else, and your life will be over. Either because you are dead, paralized or worse yet in prison for killing someone. The things we plan for rarely kill us, it's the things that were unplanned that do us in.
Love your car though