Harry,
You have a valid point here, the problem remains or may get worse if your running the timing out of a dist. - there are 2 sets of gear back lash + the chatter the oil pump puts back into the dist. shaft. One would think all this will change the timing. For a low state tune engine it might be hard to discern. For a high output motor that is sensitive to small tuning changes its probably measurable on a inertial engine dyno.
On the 4200 GM knew of this problem and place the crank timing wheel between #5&6. My guess is they determined that this was as close to the neutral point in the crank when the TC mass is taken into consideration.
