What were the original donuts made out of? I've seen steel for sale and other materials. My friend's shop has some made out of asbestos. And what would be the best to install.
Agree with Jim regarding steel gasket "donuts". However, the fiber gaskets definitely make tightening up the H-pipe a little easier since there is a little bit of flex as the exhaust manifold and H-pipe seal.
In addition, you need to carefully inspect the exhaust manifold flange for any damage (ask me how I found out - yes it was the hard way
). Upon close inspection, my drivers's side exhaust manifold had a broken stud at some point in it's life and when they drilled and machined out the broken stud they ever so slightly enlarged the flange that seals against the H-pipe. As a result, the fiber style exhaust gaskets didn't seal and burned right up (and steel ones didn't effectively seal / fix the problem either). Provided you have a clean and undamaged flange - either exhaust manifold gasket will work just fine.