Idle went nuts.

I actually just bought a (much) more expensive camera at the local parts store. "Looked" in the intake and didn't see too much. But I used the little magnet attachment and pulled a small, and totally unidentifiable, piece of metal out of the #1 cylinder intake. There is no doubt that the bolt and nut went into the cylinder(s). I've been reading the slantsix.org stuff - thanks! I'm also taking a bunch of pictures of everything. This engine has a header on it and some kind of frame-harness over the intake and header that does not appear in any of the pictures in the manual.

Unfortunately, it's been raining cats and dogs for the last two days so I haven't gotten to pulling the intake or looking in the spark plug holes. But I have almost zero doubt that the head's going to have to come off. If there is damage to the head and/or cylinders, it's going to raise some questions about what to do next... replace the slant six or go with a small block.

If, on the other hand, I get really lucky, I have another small Holley 2 bbl carb that should be available to raid to replace the damaged throttle blade.

Will update as soon as I have more info.