I tend to keep old parts that are 'ok' that I replace, for a while, "just in case". These were a couple of the leads I replaced when I had to pull everything off the top to replace an injector that failed, and a couple of the, still working ok, plugs I replaced a couple of years ago. (So much for keeping them for 'a while'...
)
Still had them in the boxes of the NGK ones I put in that are working perfectly. Took me ages to figure out which were the best ones for the 3.8 that suited it. I'm pretty sure I sourced them from the US on eBay (Oz version), as it was less than half the local cost.
Rockauto.com is a great place fot standard parts, shipping can be expensive as they send by courier, but you usually get the bits within about a week.
Good to hear that you have it pinned down!
