Engine / Trans. Knock

Was out yesterday doing a little performance driving (30 mile curvy stretch), I was really pushing the car to it's limits.

At one point I came to a stop and noticed that I had a "knock" noise coming from the firewall area. It doesn't knock from idle to 2200RPM. Also, I can feel it in the stick, which leads me to think something in the area of the flywheel/transmission.

It definitely sounds like its located in the very rear of the engine or the front of the transmission.

My fear is that it's something more than replacing the clutch or throw out bearing or something along those lines. Please don't tell me I spun a bearing inside the motor...

Any help/suggestions are very appreciated!

Ok, just went out and started digging around underneath it while it was running. It seems more and more like it's coming from the top back part of the engine, it can be heard faintly at low RPM's with your ear almost agains the motor, then pretty loud above 2200 or so.
Does somebody have a large truck I can jump in front of???

think i've got it figured out

rod bearing, or something of that sort $$$$$$$$ anybody have an idea on cost to have a shop take care of it?