I couldn't say how it would run unindexed... but its easy to do. I just put a sharpy mark lining up with the open face of the electrode. I believe the last time I changed mine they practically line themselves up automatically when tight.
I have done BKR7EIX plugs (iridium version and half the price of the stockers) and are not indexed...
Have seen ZERO difference on start up, idle, HP, rpm, drivability...
just saying-BJ