Yeah, I did the same thing to my freshly rebuild motor. It was when I was putting the intake manifold on. It sucks having the motor go under the cowl. Heard something drop, looked around but didn't see anything. There was a huge backfire when I started it. Valve cover gaskets blew out, dipstick blew out. I felt like an ***. It was a very expensive lesson.

My block was cracked too. Heads were damaged but salvagable. To me the ability to install everything on the motor is one of the advantages of installing the motor from underside of the car.

 

Exactly what bolt/nut fell into the intake port? I didn't think there was anything that could do that, unless it was something that happened while the intake itself was off