^ Generally speaking, platinum plugs are more friendly for extended "change intervals" and most guys still like the tried and true copper plugs for performance. Copper means you'll have to change them a little sooner than a platinum plug, but if you're a gearhead who wrenches a lot that's usually not an issue.
I'm not sold on the fancy high dollar Iridium (or other precious metal style plugs) due to their high cost ratio - that's money that could be better spent elsewhere IMHO if looking at cost-per-performance. But, if you have a lot of disposable income and feel the need for "high end" sparkplugs, go ahead and purchase them.
Not sure about number of quarts of oil for your supercharger application. The owner's manual should call for 6 quarts naturally aspirated. Might want to check the
Vortech website to see if you can find any literature regarding the oil issue when running their superchargers or maybe contact their tech support.
You could also monitor the oil level (preferably right after an oil change, so you have a "known" starting value) to see where 6 quarts "rates" at on the dipstick (assuming the dipstick reads accurately). For example, if the dipstick is reading "low" after 6 quarts are added after the car has been sitting for awhile, then you can safely add another quart or so and have a better feel for the number of quarts to use.
If possible, try to contact the previous owner for more info about the tune and sparkplugs if you can. They might have been running one range "colder" of a sparkplug possibly. Pulling a few of the plugs currently installed should give you a good clue as to what to run (re-check the gap) as well.
If you want to be really safe and thorough, take the car to your own dyno tuner if you want to get everything "just right."
G'luck
