asked about that on here several years back and was told its not worth the bother. In case you're wondering, "indexing" plugs mean you mark which way the tip is pointing and use washers (or other means) when you install the plugs to ensure they all line up in exactly the same way in the cylinder (wrt to where they point).
Z-Jay Edmonton Z Car Club 93 300ZX TT - Stage VI 01 Sentra SE - daily driver