gjberche,
Your are right on the money, and of course who could doubt the shop manual.
That screw is difficult to access. If the plate bolted to the block (octane selector) is centered in its slot and the engine is then timed to the ball or mark using the troublesome clamp, then any subsequent timing issues can be addressed with the bolt/slot in the vacuum advance plate.
I guess my thought was that the clamp screw was so difficult to get to...why use it! Use the bolt and slot in the hold down plate.
When the distributor is removed with all the hardware still attached, it allows you to reinstall close to the original position...the hole where the bolt goes lines everything up for you. This only applies if you locate #1 and reinstall accordingly...but we all to that!
The advent of the modern timing light makes things quite a bit easier.
Stuart
