You can get indexing washers from Jegs, Summit, ect. They're basically a shim that goes on the plug seat to change the position of the ground strap. If for a tapered seat plug, they're cone shaped, and flat for a gasketed plug. They look like a gsket and come in various thicknesses......I prefer to buy several sets of plugs at a time and find the correct one for each hole by trial and error. It can take a while and be kinda frustrating, but it beats smashing a plug at high rpm....the washers work fine though. I just don't like the idea unless I'm in a hurry.....or already tried 20 plugs and still haven't fould one that will work!!