I have pretty good experience with Amazon. I got some new Moog ball joints as part of fixing up the truck and they're great. Amazon has a garage feature that tells you about fit. But generally check the brand/store first. Moog is quality. For tailgate cables I'd think it would be pretty hard to go wrong.
Like I said though you can probably get them cheaper at a brick & mortar store (or autozone.com, O'Reilly, Advanced Auto Parts). Mine came right off the rack; they're not a special/unique item at all. Looks like they might have been $10 at Autozone.