I remember years ago I was selling a sbc motor. It was just resting on a dolly, a perspective buyer wanted to start it up, on the dolly. I was like, yeah I don't think so.
I've started engines up on the floor but NEVER rev'ed it up like he did. Also, starting it up with a flex plate is STUPID. I have an old 11" flywheel and put a bell housing on it for safety. Also letting it run without a radiator for that long can do a lot of damage in a short time.
Semi OT but kind of related (sorry if a repost):
Another way to start your V8 could to be loose on a pallet in the back corner of your garage. http://www.youtube.com/watch?v=JHGRfouL6DM
It is a 14 litre Scania Truck Engine that had been sitting for about 10 years according to what
is said in the vid, it starts up at about 2:30 but the first minutes are a prelude to what happens then.