Red92s, Yes a 6" extension will put the ratchet just above the a frame, this is easier done from under the car. I use a brazing tip on an oxy/acetylene torch to heat up the nuts to make their removal easier. Run a dei over the threads that you are reusing to clean them up. Don't forget to use some anti-seize on the install to make your future brighter.

Agent -Strangeglove, My best guess is you will have to cut the spinning bolt with a hacksaw, either hand or milwaukee. If you can, drive a thin wedge between the manifold and the pipe to apply enough pressure to the bolt while you cut it. Replace the damaged thread with a heli-coil or you may be able to drill right thru and add a nut to the bolt for closure. I personally prefer the nut bolt combo to a stud.