yeah i also have used plugs like that in my old nova, they was good plugs for lots of NOS they would light up about any thing , however they wore out faster then normal plugs, but they would last about a season so it was worth it.
as far as indexing goes we also do that on most our drag car motors, what it does is makes sure the spark isnt shrouded from the strap in any way, you get the indexing washers and mark where the strap is and when you install the plug you want the open space facing into the chamber. i will admit we havnt seen any major help in doing this however my dad is old school and is stuck in his ways.