they make nuts that go over stripped nuts. The tool looks like a regular nut except that inside it had 4 rounded edges that grab the stripped nut. You then use a larger socket to remove it.
I bought that tool from either Harbor Freight or Sears not sure. They also make a nut cracker that you bind the nut and break it off (never used one). If you have room you could try a saws all or hacksaw.
When taking off old rusty nuts I use 6 point sockets. Make sure you are using the right size too. It is a pain in the butt, but there are many metric nuts and bolts on the mustang.
Hope some of this helped. I may be able to find the package the nuts came in and give you the exact name and brand I used to get my H-pipe nut loose. (I stripped one on the passenger's side near the starter motor.
I'll look when I get off work at 6am CST.
Aaron.
Ps PB Buster works pretty good too. Try spraying em down and giving em a few wacks with something to jar the juice around.
