I agree with Al, you might want to leave a few inches of space for such a beast of a locomotive to clear the corner.
The 2-10-10-2, I believe, isn't the largest engine lionel has made. The S1 is exactly 1 yard long for example, but the super santa fe type(as I like to call it) is still a massive engine.
As for which one to purchase, I'd personally go for the Blackbonnet but that's your choice
I think your best bet for finding one at a good price would be trainworld or charles ro.