I mainly know from autox my car, and hitting the stock "rev limiter" alot. Now I have an MSD limiter, set at 6100. If I hit it, the stock tach will show about 7000.
Later on, after getting my car dynoed a few times, and seeing other Fox stangs get dynoed, the driver will stop the pull at an indicated 6000 rpm, and the dyno print out will show that power was cut around 5200. To get a dyno pull to a full 6000 rpms, you need to let the stock tach climb to around 7000. The tach seems to get more inaccurate at higher rpms, its possible FORD did this on purpose to ease warrenty issues.