I've seen this subject come up a couple of times over the years, even seen some pictures......IIRC the "Mountaineer" was a package marketed by either a single dealer or a group of dealers out West, maybe Colorado? The package consisted of graphics, larger tires (can't remember size), and custom wheels. If you're any good at the search feature you may be able to locate those old threads.
The YJ is no longer my DD. I have sacrificed all future retirement plans for jeep parts. I'm depending on social security!