Hello, Racer. Nice to see you here. It's very sad to hear that you will take time from this community.
Maybe it's due to not too many responds to your post. So I decided to give you answers as much as I can. (Even though my English is not a native speaker level.)
My thought on Mountain Rushmore. Hmm..... I would value this with 3 categories.
1. Influence on the business
2. Work rate
3. Drawing ability
The very first wrestler I come up with, is definitely Rikidozan. He created Japanese pro wrestling by himself.
His philosophy transferred into his successors, Inoki and Baba and it became the famous Strong style and King's Road style.
He made all the basis of current Japanese pro wrestling too. Hard training, excursion, using foreign wrestlers, promotional war, etc etc.
Nobody can touch his influence in the history of pro wrestling, and his work rate was amazing too.
Of course he was the best draw at the time, and he still has the best tv rating record in Japan. I guess it was 86%.
I would go with El Santo, for making Mexican wrestling.
For American pro wrestling, it's tricky. Probably Hulk Hogan for the drawing aspect and influence.
For work rate, I can think of Ric Flair. But hard to say that he influenced the business a lot.
Flair was the best worker for his generation, but he was pretty much old school. Far from a revolutionary style.
Maybe Dynamite Kid for creating modern pro wrestling style (High flying, agile, fast-paced style)
and having the best work rate along with Tiger Mask 1.
So my choice would be, Rikidozan, El Santo, Hulk Hogan, Dynamite Kid (Or maybe Ric Flair)