It depends on the shape of the pipe, and the hole in the manifold. The donut gasket is used if there's a chamfer on the inside diameter of the manifold port, and a corresponding taper in the exhaust pipe. Earlier applications had a flat flange welded onto the pipe, with a flat surface on the manifold. Use whichever gasket fits the specific application you have, not both.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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