That's pretty exciting news!
Who owns the Casey Jones? Is it in running condition? If so, are there problems or restrictions with using it? Probably it's too much of a treasure to use on a regular basis. I'm assuming there must some issue with it if you're looking for other resources.
Aren't there a couple of NG Porters that have been for sale for years east of Denver? I don't recall their gauge, and they are probably overpriced.
I think a "motor" (goose) would be a great idea, and probably one of the less expensive options.
Norm in Denver