I'd consider 11ft the minimum for a lift, 12 to be good and 13+ to be optimal.
I have about 11.5 and a 4 post it takes about 11ft of that to get the car high enough to walk under (6'1).
But that's only half the issue, most likely you own other cars that won't be a mustang which is relatively low compared to an suv.
Just keep in mind, mine is in an attached garage that I go in every day, walking around a lift with a car on it gets old real quick.
It's also a 4 post, so you lose 5 inches for the ramps.
The good part about a 4 is you can safely park under it or on it anytime quickly and easily (which I do, but I don't let my wife).
The down side is to get the wheels off you need a $1000 slide jack, per end.