Have you had a chance to remove your pulley? Is there any damage from running no harmonic balancer?
My previous owner decided that he would not run a harmonic balancer when he rebuilt the engine (actually that is a bit tongue in cheek, maybe he didn't know what he was doing when he welded it). My crank is not nearly as disastrous as the broken crank (well at least I hope it isn't, will know when I pull the crank tomorrow), but the welded balancer definitely was moving at a different frequency to the crank.
Oh yeah the key is actually in the keyway in the following picture.
This was in a turbo motor not revving much above 6000rpm, I guess not balanced as well as any of these high revving motors in this thread.