I'll try to find an article on that. I only found a Wiki reference to a railroad train which would've gone through the mountain itself as well as around the area lol
Point is, I remember reading that an early concept for Grizzly Peak included a very similar ride to Big Thunder Mountain that was never built because apparently the mountain wasn't built to hold the weight of two attractions (and the land was over budget, as well). The concept returned much later as Big Grizzly Mountain Runaway Mine Cars at Hong Kong.
Not sure if that was a fake article, but I sure remember reading about it.