Your local parts houses buy direct from the manufactures and or distribution centers, so no (or not much) chance of getting counterfeit parts…
Rock auto buys whatever from left over stock and I don’t even know where, but those “close out” prices make me a little nervous…
If you buy online at O’Reilly or Advance, they always have a coupon or something, and you can even do a store pick up or if $X amount they ship it free to your house, and if there is an issue, simply take it to the store for warranty or return or whatever… Yes I use Rock Auto at times, just watch the shipping charges…