I index mine in the cuda...906 iron heads{oversized valves} on the 440...I run them straight up at 12:oclock position...They definitely look much cleaner and the "shadow" from the electrode is gone in this position...I have the index washers but I usually just buy a bunch of plugs then sort them out so I don't need to use them... ..I'm right around 500 HP and it seems to idle/run better with them indexed...FWIW..