I think the stock gaskets are probably fine. On some cars, you hear of guys blowing the gaskets. In most cases, it's actually from deto. Since their rods are stronger, the first part to fail from deto is the head gasket. Using a stronger head gasket will often make you live through the deto until it kills your rods. Therefore, some people try to fix the deto, and use the stock head gasket as a "fuse".
In our case, the rods will break BEFORE the gasket. That's why I think we never see failed Zetec gaskets.