How abokut indexing the spark plugs?
Which way the open end of the gap faces is another interesting subject.
We used to look at the open end of the plug and put a magic marker line on the white part of the plug and then insert different sizes of copper washers under the plugs to get the open end to line up in between the intake value and the exhaust value.
After doing many dyno tests trying different plugs we found that the job of a spark plug was to fire at the correct time very time.
Now how long the spark fires for is a whole different story which leads to a much cleaner burn of the fuel.