[Synchro909]

I'd try a small dab of silicone on that divot. Vacuum will hold it in place if vacuum reaches it, it is flexible and withstands temperatures way in excess of what you will get on an inlet manifold. Heck, I've seen no manifold gaskets at all (exhaust included) on a Model A, just silicone and the car ran like a champ.
Don't over think it.