This is probably the cage I will be going with when time comes if I do not make my own. I've heard a lot of good things about this company and their work seems to be top notch. I just glansed over the rules on NHRA's site about cages and it seems to be legal. Hell, its even cheaper than that Kenny Brown thing that got posted up earlier.
http://www.wolferacecraft.com/install/must/snbar.aspx
another link to the actual price
http://www.wolferacecraft.com/detail.aspx?ID=288
go up to the Mustang tab at the top and you can look at all their other bars/cages for the car as well