+1
AC Delco hasn't made a spark plug in over 30 years.
Copper plugs have a wider heat range than non copper plugs.
Platinum plugs last forever (100,000 miles+). Iridium plugs last 3 times as long.
How long it 3 forevers anyway?
Bosch had the first platinum plugs for less misfire. At the time they were fighting emissions and were trying to reduce misfires that jacked up the HC emissions. The platinum needs less voltage to jump the gap so more current was available to start the combustion event reducing misfires in the leaner air/fuel mixtures they were trying to use.
The fine wire tip is used to blast away contaminants to keep the firing tip clean. This allows a colder heat range plug to be used reducing the chances of preignition without fouling the plug.
Waste spark ignitions fire one plug from the center to the side electrode it's companion plug fires backwards.
Double platinum plugs work well with this type of ignition.
Double platinium, iridium, ruthenium & etc. work fine with distributors and coil on plug or coil near plug ignitions too but they are no better than the single platinum for those applications and generally cost more.
E3 plugs and SplitFire plugs (now deceased were made by Autolite) do the same job as side gapping the plug (cutting the side electrode back enough to make the spark jump sideways).
I have been side gapping plugs for 45 years. Side gapping MAY help combustion by not shrouding the flame kernel started by the spark.
It acts like advancing the timing without advancing the timing. Unshrouding the flame kernel burns more of the fuel nearer TDC when the piston has better leverage on the crank.
That effect MAY help power, engine life, fuel economy, and tailpipe emissions.
Some engines respond well to this, some are totally insensitive. A larger plug gap can have the same effect.
Projected center electrode plugs also have a similar effect.
Indexing spark plugs is a good practice. Indexing puts the side electrode away from the piston so it doesn't block the flame travel. Again some engines may not care if the plugs are indexed but I have never seen it hurt performance.
With a domed piston it is mandatory to prevent the dome from contacting the side electrode.
Do not use projected plugs on a supercharged or nitrous engines. The longer side electrode is the problem because it may stay hot enough to cause preignition.
When I start an unknown combo I put the coldest plugs that don't foul.
I would rather sell you 3 sets of plugs than a second set of pistons.
Choose the plugs you like best, tune it until you're happy with the performance, close the hood, and go get ice cream!