I'd just do some basic platinums, and be more focused on the part number than marketing metal. Coppers would be fine if you are expecting to only have it for another couple years, because they need changing every few oil changes. Platinums will be good typically for 5-10yrs, but cost a bunch more. Double isn't much of a big difference.
Given your choices I would just go with the regular platinum plugs despite the 3800 being a waste spark system. That only gives spark plugs half their life expectancy. For instance a 100,000 mile plug you will want to change at 50,000 miles.
Just make sure you get the correct heat range & they are properly gapped at .060"
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