Anything Railking will run on O-31. My RK Big boy, Challenger, and cab forwards all do without issue. Just be mindful of the overhang needed for track side items to clear on a curve.
This all true but the Lionchief Big Boys cost $300+ more vs. the MTH imperal model. My Imperial Big Boy came with three refer cars and a caboose for $729 back in 2018. I priced a LC2.0 version that was just the loco for $1079.
I was also able to upgrade my Imperial BB with a quillable whistle at no cost.
Not sure how this turned into an MTH vs. Lionel discussion. That was clearly not my point.
I was simply responding to a poster who intimated that he could not run Legacy steam on 0-31 curves and/or was limited to 0-6-0's and Camelbacks. Another poster responded that there were many varieties of Legacy steam that would run down to 0-31 and I was simply adding an additional option for the poster for an LC+2.0 Big Boy that would also run on 0-31 curves and is compatible with the Legacy system (as opposed to other models in the LC line-up).
Congratulations on your Imperial Big Boy.