Sorry to be a spoilsport here but I wouldn't recommend thread restoration (chasing) for this particular situation. Your seat remaining attached in an accident is critical to your safety. There is another good solution though.

You want to install a Helicoil. Buy the proper kit. It comes with a drill, tap, helicoils (4 I think) and an insertion tool. You'll drill out the hole, tap it with the special tap, install the helicoil (which is like a spring and threaded on both sides) and the hole will be stronger than new. Follow the supplied directions. It will take about ten minutes.

 

I'm going to drop by the dealer and pick up a longer nuts and run it right through the chassis and then secure it with a nut on the other side. That should be enough.