Since the PCM determines the ignition event from the position of the cam (the optispark is directly connected to the cam), using an offset crank key does not affect that relationship. I'm not sure how it would be affected by using an offset cam bushing.

 

I dont think it would make any diff. doin the crank key or the bushing.
it does the same thing. change the relationship of the crank to the cam position.
and to someone who said you shouldnt adv. or retard the cam because the opti timing would be off, I dont understand your logic. if that was true, then we wouldnt be able to isntall a cam with diff. specs then stock, or the timing of the opti spark wouldnt be correct.
and another thing, when you advance/retard the cam to put it on the recomended centerline, your not really retarding it, your adj. it so that the cam is in the correct position. to leave it off by Xdeg. would be leaving it adv/retarded. know what I mean?
I wish I would have bought the tools to do this back when I was assembling my engine. I would have def. deg. the cam while it was on the engine stand. I recently installed an LS1 cam that was off by 3 deg.. I used an adj. timing set (comp cams) to correct it and double checked it after that.