depends what gears they have, with my 3.08's I can hit approx 165 at 5 grand in third gear.... if they had 2.73's I don't even wanna know what speed they are going lol.
A cam would be useless on a basically stock engine IMO. An intake would do so much more for you. As far as heads go, what are your plans down the road for it? What are your hp goals? These will all be the deciding factors.
I've pinned the needle trying to power shift and didn't hit the rev limiter. I'm sure that the stock tach is just something to be left to the imagination when guessing rpms. So don't worry about it. Although I would try to keep it under 7 grand next time :D
I thought that when you go open throttle, the O2 sensor "shuts off" and the injectors just blast fuel, causing a rich condition, which then causes back smoke?
I believe they are controlled by the computer. It will not let them rev too high before it shifts into next gear. You can just shift it manually if you want to get than extra bit out of it.