[Drbrown]

I use a wire gauge to test gaps and as said above, file the electrode so it has a flat top. Once clean and tested under compression for performance, I personally have never worried about mixing plugs among the different cylinders.

Two options re individual fouling plugs: Replace all the plugs with hotter plugs which seems to be the standard procedure, or if one or more cylinders are by-passing more oil than the majority of the others, some economy-minded "old-times" I knew would just put a hotter plug in that/those particular cylinder and keep track of its proper location when reinstalling, and then just clean-up and reinstall the plugs that are still in good condition.

Gap adjustment: I have no personal experience with this but in working with Bubba and others re distributor set-up, I understand that plug gap may effect the performance/life of electronic modules in distributors. (coils too?)