340 Exhaust Manifold Bolts
If you are a cheap bastard, you can slip in reasonably thick wall tubing sleeves that end up protruding out of the manifold holes a wee bit, and using grade 8 5/16 coarse thread bolts EXACTLY the right length.Shim with washers to taste.Hint: they have to be IN the holes when you slip the manifolds down in the bay against the heads (cant do it with them in there, not enough room)