Well theoretically you could, but that doesn't mean its a good idea. There really is not reason to do so, unless you've got the car built to make power past 6K. The limiting factor is the crankshaft.
Also the stock gauges are known to be off a bit, so I'd be very careful when spining the engine that high. What do you have done to the car thus far?
2000 Mustang GT-Former giggle gas addict
1990 Mustang GT w/ Vortech V3
***resident gun idiot***