Exhaust Manifolds do not use gaskets because gaskets cause warping, cracks, leaks, & rust. Ford originally used chassis grease (which carmelized like cast-Iron cookware into a non-stick surface), but modern high-temperature silicone is at least as good. The manifolds should be planed first, though. These were sandblasted, painted inside & out with ultra-high-temp paint, and then planed.
IF THE IMAGE IS TOO SMALL, click it.

This shows re-used aftermarket manifolds:



These show the bolts, studs, & nuts:

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For the whole process:

Owner caption May 2021 · Photo 0 of 5000