Alright, finally giving you guys my two cents! This was SO amazing to read!! While the original movie script wasn't all that different from the finished movie, this one was another story, and I mean that literally!

Firstly, I'd love to see how this script's solar-system opening scene would have played out. I always loved the space-focused LBT openings--they were so gorgeous. This one really had potential to be among the best of them, with the script mentioning nebulae ("astral clouds") and even specific constellations!
Moving on to Grandpa Longneck's "Great Dinosaur" story, the sharptooth appears much fiercer than in the movie, actually shown grabbing and swallowing a Psittacosaurus. I wouldn't have minded that being kept in there, especially since I'm not recalling a Psittacosaurus ever being shown in LBT before. (I always loved it when these movies expanded their range of species!) Also, this version of the battle between Doc and the sharptooth felt more parallel to a classic Wild West showdown, with emphasis on long shadows and a "spaghetti western rattle" at one point. Could've been fun to keep it that way.
The characters saying that Saurus Rock "wears a necklace" was a bit weird, considering that "necklace" seems too much of a modern word to be in their vocabulary. I'm glad they changed the final version to "a circle of teeth around its neck." There are some similar slip-ups throughout this script, like Cera mentioning her dad serving kelp for dinner. I can't believe they wouldn't have their own word for "kelp" in LBT...wait, come to think of it, they eventually did. By the TV series, they made it clear that seaweed and other underwater plants were known as "water greens." But I guess I'm going to chalk up this kind of thing to the writers figuring they'd work out basic dialogue first and mess with rewording later if they needed to.
(It really annoyed me, though, that this script kept referring to Ducky as a boy.

Who could possibly mistake Ducky for a boy? Hadn't these people seen any LBT movies?)
I think I prefer the final version of Doc's first Valley appearance. They had Mr. Threehorn being the only character who was wary of him in the movie, but here Doc comes in and helps everyone gather leaves, and suddenly all the other adults are like, "WHO IS THIS STRANGE GUY?? I'M SUSPICIOUS!!" Overreacting much?

Even Grandpa Longneck is unsure--what gives? Since when is the whole Great Valley so xenophobic? However, I do like the way Doc began this script as a quieter type of hero. He doesn't do any dramatic rescues or impressive tail whips (though his tail-whip attack on that leaf in the final movie was really cool). Instead, he puts himself to work harvesting the Valley's leaves all through the day. He's a hardworking guy who quietly does what he can for his community, more the type of hero you'd see in "The Andy Griffith Show" than a western action-adventure. It's more ambiguous whether he really is the dinosaurs' hero of legend or not, whereas the final movie makes it pretty obvious early on that he's the Lone Dinosaur.
It's funny here that
Spike, of all characters, is the one who decides the Gang should go to Saurus Rock.

Yeah, I can't quite see that happening...this is where I'm gonna bring up Dana and Dinah. I know a lot of people don't like them and have wondered why they were added to the movie at all, but I think they had a purpose. Whenever the Gang leaves the Great Valley, it's usually to help/save someone else: getting Ducky's unhatched sibling back in II, finding water in III, healing Grandpa in IV, and so on. The original version of this script, however, has them going to Saurus Rock just for the fun of it, whereas Dana and Dinah taking off meant they had a real reason to go. I personally never saw what was so annoying about Dana and Dinah, anyway, but I guess that's just me.
I love the concept of the original Saurus Rock--I can just see it, a Frankenstein-ish mashup of all kinds of different dinosaur species! Now, THAT would've been cool! And the way ominous things start happening right after the tooth is broken, it's really like we're looking at the wrath of some powerful ancient magic! That would've been pretty neat for an LBT movie!
I wonder if this forest they keep mentioning is the same forest the Allosaurus finds the kids in during the final movie? Whatever the case, I love the idea of four Ceratosaurus being this movie's sharpteeth so much better! Ceratosaurus is such an underused species, and I would've loved to see not just one but FOUR in LBT! Every scene with them here is great! Though I can't really imagine the part in one chase scene where Petrie holds back a tree to catapult the Gang across a canyon. LBT often defies physics, I know, but little Petrie holding an entire tree down? Nope. Not happening. And the sharptooth battle towards the end of this script has me wondering how long a carnivore can plausibly hold its prey in its grasp without eating it, but that was an exciting scene, regardless, and moments like Littlefoot riding a makeshift "bobsled" were fun. I will say, however, that the mentions of snow and ice kept weirding me out--it's very difficult for me to imagine snow in any pre-VIII LBT movie!
I was surprised that Doc wasn't in this version of the movie all that much. It's more about the bad luck curse than anything else. Doc's screen time in this script is comparable to the Rainbow Faces' in LBT VII--hardly any, compared to most guest characters. It definitely would've added some mystery to the character if they had gone through with this, but the eventual increase in his screen time did a lot to add to the western feel of this movie. The change of name from "Great Dinosaur" to "Lone Dinosaur" was also a more obvious homage to westerns (i.e., the Lone Ranger). While I'm still talking about Doc, something else I noticed was that he comes across a little less...grumpy, I guess, in this version, which isn't a bad thing.
The "magical" assimilation of the sharptooth's tooth into the rest of Saurus Rock confirms the monument as an actual magical entity towards the end! An outrageous moment for LBT, sure, but my young self would've been absolutely wowed.
Overall, I can't decide which version of this movie I prefer! I mean, the fact that I grew up with the LBT VI we ended up getting makes it hard for me to imagine it any other way, but the way this script took things in a spooky/supernatural direction pulled me in. I'm so glad I got to read this! It would be so awesome if other early scripts like this got discovered someday (*cough*VII*cough*)!