Sounds kind of like some sort of bushing, or bearing. Does the engine have a cast crank, and if so, does it have the proper flywheel, and balancer? I'm in Morristown, maybe we can get together and figure it out.
Hey, that's very gracious of you. I'd kill for access to a lift right now. :-)
Darn good question on the engine and I don't know for sure, but when I got the engine in shipping, I took pictures and posted on the FBBO forum and asked others' opinions. The consensus was that it was forged and since it came with those types of balancers and flywheels, I called it good.
If the problem was a gradual harmonic vibration that became stronger (or lesser) with speed, I'd certainly be looking at that possibility, though, sure - but it isn't, as you can hear.
This comes on all at once with a certain speed.
