intake/exhaust mounting, what am I missing?

From what I see, you're missing a nut like the castle nut on the right and the two brass washers that go on either end of the exhaust manifold. They have an inside bevel on one side that the castle part of the nuts fit into. Also, when you install the bat wings, it's imperative that you don't allow them to touch the manifolds other than where they tighten up against the manifold. If that makes sense. Only 10 - 15 LB FT on torque. THey don't need much. Lastly, when you install the studs into the heads, use some sort of sealer. Some or all of the stud holes go into the water jacket. I've seen some have all the holes into the water jacket and some have a few blind holes. I use RED high temp RTV, because it seals and also acts as a anti seize and does not allow them to rust into the head. That's what I use and it's always worked for me.