Not convinced.
"Timing chains can slip over the years".
Chains don't slip. They develop slack and slightly retard the cam (which reduces pinging), or skip a tooth.
"4. Keep in mind when adjusting the timing, you have to turn the distributor clockwise to advance and counter-clockwise to retard."
Or, turn the distributor clockwise to retard and counter-clockwise to advance. See - there is more than one engine?
"5. ...look for a maximum reading on the gauge. For instance, if the reading on your gauge peaks at 18 inches of vacuum, that is the maximum for your engine."
Never, it will always be higher at 1,500 RPM than idle.
"(The normal range could be from a high of 20 inches to a low of 15 inches, depending on the internal condition of your motor)."
Or, between 5 and 25 inches, depending on the engine.
"Turning the screws in will cause a richer mixture, turning the screws out will cause a leaner mixture.".
Or, turning the screws out will cause a richer mixture, turning the screws in will cause a leaner mixture depending on the carburetor.
In summary: you use vacuum, then you test to see if it pings. Then you retard it as needed - exactly as the stock settings.
